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WHAT IS CLAIMED IS:
1. A piano graphic printing plate precursor comprising:
a support;
an image recording layer formed on the support; and
a water-soluble compound having a molecular weight in a range of 60 to 300 and a solubility of 10 g/L or greater in water at 20°C,
wherein a content of the water-soluble compound per unit area in a region on the image recording layer side from an end portion of the planographic printing plate precursor to a portion inside the end portion by 5 mm is greater than a content of the water-soluble compound per unit area in a region other than the above-described region by an amount of 50 mg/m or greater.
2. The planographic printing plate precursor according to claim 1,
wherein the water-soluble compound is a polyol, a betaine, an organic sulfonate, an organic sulfate, an organic carboxylic acid, or salts thereof, or an amino acid.
3. The planographic printing plate precursor according to claim 1 or 2,
wherein the end portion of the planographic printing plate precursor has a sagging shape in which a sagging amount X is in a range of 35 lo 150 pm and a sagging width Y is in a range of 70 to 300 pm.
4. The planographic printing plate precursor according to any one of claims 1 to 3,
wherein the region on the image recording layer side from an end portion to a portion inside the end portion by 5 mm further contains a hydrophilic compound.
5. The planographic printing plate precursor according to claim 4,
wherein the hydrophilic compound is a compound which includes a support-adsorptive group.
6. The planographic printing plate precursor according to claim 5,
wherein the compound having a support-adsorptive group is a phosphoric acid compound or a phosphonic acid compound.

7. The planographic printing plate precursor according to claim 6,
wherein the phosphoric acid compound or the phosphonic acid compound is a polymer compound.
8. The planographic printing plate precursor according to any one of claims 1 to 7,
wherein the image recording layer contains an infrared absorbent, a polymerization initiator, a polymerizable compound, and a binder polymer.
9. The planographic printing plate precursor according to any one of claims 1 to 7,
wherein the image recording layer contains an infrared absorbent, a polymerization initiator, a polymerizable compound, and a particulate polymer compound.
10. The planographic printing plate precursor according to any one of claims 1 to 7,
wherein the image recording layer contains an infrared absorbent and a thermoplastic fine particle polymer.
11. A method of producing a planographic printing plate precursor which includes a support;
an image recording layer formed on the support; and a water-soluble compound having a
molecular weight in a range of 60 to 300 and a solubility of 10 g/L or greater in water at 20°C,
in which a content of the water-soluble compound per unit area in a region on the image
recording layer side from an end portion of the planographic printing plate precursor to a
portion inside the end portion by 5 mm is greater than the content of the water-soluble
compound per unit area in a region other than the above-described region by an amount of 50
mg/m' or greater, the method comprising:
(a) an image recording layer forming step of forming the image recording layer;
(b) a coating step of coating a part of a region where the image recording layer is formed by the step (a) with a coating solution containing the water-soluble compound such that the coating solution and the region overlap each other; and
(c) a cutting step of cutting the region coated with the coating solution such that the region is in a range from the end portion of the cut planographic printing plate precursor to a portion inside the end portion by 5 mm,
wherein the steps are performed in order of the step (a), the step (b), and the step (c)

or in order of the step (b), the step (a), and the step (c), on the support.
12. The method of producing a planographic printing plate precursor according to claim 11,
wherein (d) an undercoat layer forming step of forming an undercoat layer is performed on the support before the step (a).
13. The method of producing a planographic printing plate precursor according to claim 11
or 12,
wherein (e) a protective layer forming step of forming a protective layer is performed on the image recording layer after the step (a) and before the step (c).
14. A method of producing a planographic printing plate precursor which includes a support;
an image recording layer formed on the support; and a water-soluble compound having a
molecular weight in a range of 60 to 300 and a solubility of 10 g/Lor greater in water at 20°C,
in which a content of the water-soluble compound per unit area in a region on the image
recording layer side from an end portion of the planographic printing plate precursor to a
portion inside the end portion by 5 mm is greater than the content of the water-soluble
compound per unit area in a region other than the above-described region by an amount of 50
mg/m' or greater, the method comprising:
(a) an image recording layer forming step of forming the image recording layer; and (r) a coating step of coating a region, from the end portion of the planographic
printing plate precursor to a portion inside the end portion by 5 mm, with a coating solution
containing the water-soluble compound,
wherein the steps are performed in order of the step (a) and the step (f) on the support.
15. The method of producing a planographic printing plate precursor according to claim 14,
wherein (d) an undercoat layer forming step of forming an undercoat layer is performed on the support before the step (a).
16. The method of producing a planographic printing plate precursor according to claim 14
or 15,
wherein (c) a protective layer forming step of forming a protective layer is performed on the image recording layer after the step (a) and before the step (f).

17. The method of producing a planographic printing plate precursor according to any one of
claims 11 to 16,
wherein the coating solution containing the water-soluble compound further contains a hydrophilic compound.
18. The method of producing a planographic printing plate precursor according io claim 17,
wherein the hydrophilic compound is a compound having a support-adsorptive group.
19. The method of producing a planographic printing plate precursor according to claim 18,
wherein the hydrophilic compound is a phosphoric acid compound or a phosphonic acid compound.
20. The method of producing a planographic printing plate precursor according to claim 19,
wherein the phosphoric acid compound or the phosphonic acid compound is a polymer compound.
21. A planographic printing plate precursor which is obtained by the production method according to any one of claims 11 to 20.
22. A printing method of performing printing comprising:
imagewise-exposing the planographic printing plate precursor according to any one of claims 1 to 10 and 21;
supplying printing ink and dampening water; and
removing an unexposed portion of the image recording layer on a printing press.
23. The printing method according to claim 22,
wherein the printing is performed using printing paper having a width wider than the width of the planographic printing plate precursor.