WE CLAIM:
1. A negative type lithographic printing plate precursor comprising:
a support having a hydrophilic surface; and
an image recording layer, on the support, containing a polymerization initiator and a polymer compound having a structure represented by Formula 1 in a main chain and an ethylenically unsaturated bond,
wherein, in Formula 1, R1 represents an (x + 2)-valent aromatic hydrocarbon ring group, and x represents an integer of 1 to 4.
2. The negative type lithographic printing plate precursor according to claim 1,
wherein the polymer compound is a polymer compound having a structure represented by Formula 2 in a main chain,
in Formula 2, R2’s each independently represent an alkyl group or an aryl group, x represents an integer of 1 to 4, and y represents an integer of 0 to 3.
3. The negative type lithographic printing plate precursor according to claim 1 or 2,
wherein the polymer compound is a polymer compound having a structure

represented by Formula 3,
in Formula 3, R2’s each independently represent an alkyl group or an aryl group, and y represents an integer of 0 to 3.
4. The negative type lithographic printing plate precursor according to claim 1,
wherein an amide bond in Formula 1 is not a part of a urea bond.
5. The negative type lithographic printing plate precursor according to any one of claims 1 to
4,
wherein the polymer compound is a resin having a constitutional repeating unit represented by Formula 4,
in Formula 4, RA1 represents a divalent linking group, RA2 represents an (xA + 2)-valent aromatic hydrocarbon ring group, RA3 represents a divalent linking group, xA represents an integer of 1 to 4, and nA represents 0 or 1.
6. The negative type lithographic printing plate precursor according to claim 5,
wherein RA1 represents a divalent linking group bonded to two carbonyl groups in Formula 4 through a carbon atom.

7. The negative type lithographic printing plate precursor according to any one of claims 1 to
6,
wherein the image recording layer further contains a sensitizing dye having a maximum absorption wavelength of 700 to 1300 nm.
8. The negative type lithographic printing plate precursor according to any one of claims 1 to
6,
wherein the image recording layer further contains a sensitizing dye having a maximum absorption wavelength of 300 to 600 nm.
9. The negative type lithographic printing plate precursor according to any one of claims 1 to
8,
wherein the image recording layer further contains a polymerizable compound.
10. The negative type lithographic printing plate precursor according to any one of claims 1
to 9,
wherein the polymer compound is a polyamide resin.
11. The negative type lithographic printing plate precursor according to any one of claims 1
to 10,
wherein the polymerization initiator is a photo-radical polymerization initiator.
12. The negative type lithographic printing plate precursor according to any one of claims 1
to 11,
wherein the polymerization initiator is an onium salt compound.
13. The negative type lithographic printing plate precursor according to any one of claims 1 to 12, further comprising an undercoat layer between the support and the image recording layer.
14. The negative type lithographic printing plate precursor according to any one of claims 1 to 13, further comprising a protective layer on the image recording layer.
15. Amethod of preparing a lithographic printing plate, comprising, in order:

an exposure step of image-exposing the negative type lithographic printing plate precursor according to any one of claims 1 to 14; and
a development step of performing development by removing a non-exposed portion of the exposed negative type lithographic printing plate precursor using a developer.