[Designation of Document] SPECIFICATION [Title of the Invention] HOT-DIP GALVANIZED STEEL SHEET AND MANUFACTURING METHOD THEREOF [Technical Field] [0001] An embodiment ofthe present invention relates to a hot-dip galvanized high strength steel sheet having improved formability and a manufacturing method thereof. The hot-dip galvanized high strength steel sheet also includes a galvanneald high strength steel sheet. Priority is claimed on Japanese Patent Application No. 2010-281690, filed December 17,2010, the content ofwhich is incorporated herein by reference. [Background Art] [0002] The strength increase (high tension) of a steel sheet used is one of the most effective methods to achieve both weight saving and a collision safety for a vehicle body. Recently, a regulation regarding the collision safety represented by Euro-NCAP has been stricter. In order to correspond to the regulation, addition of a stiffened member or the like is required, and thus, an increase in body weight is unavoidable. The increase in body weight results in a decrease in fuel efficiency. Accordingly, the increase in a utilization of an ultra-high strength material, in which a thickness is capable of being thinned while a strength of a part is maintained, has been more preferable. On the other hand, in order to achieve the weight saving ofthe part as much as possible, a shape of the part becomes complicated. Thereby, further improvement of forming workability is required in the steel sheet. Particularly, in most cases, a high strength thin steel sheet is applied to a portion, in which bending - 1 - deformation is mainly performed, such as a side sill. Accordingly, it is important to estimate a hole expansibility which is an index indicating a bendability or local ductility as formability of the high strength thin steel sheet. Moreover, since corrosion resistance is also required in the member, a hot-dip galvanizing or a galvannealing is applied to the high strength steel sheet used. [0003] However, in general, if the strength of the steel sheet is increased, it is known that the forming workability such as the bendability or the hole expansibility is deteriorated. For example, in the related art, steel sheets having improved the hole expansibility are suggested in Patent Documents 1 to 3. [0004] Since the high strength steel sheet has much content of an alloying element and the alloying element is concentrated in a center portion of a sheet thickness, the hole expansibility is deteriorated. However, there is no related art which discloses a hardness difference between a surface portion of the steel sheet and a center portion of the steel sheet. Moreover, since a MnS having a large size becomes a fracture origin at the time of molding, it is assumed that a precipitation state of the MnS influences formability. However, there is no related art which discloses the precipitation state of the MnS. [Prior Art Document] [Patent Document] [0005] [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2005-256141 - 2 - [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2006-274317 [Patent Document 3] Japanese Unexamined Patent Application, First Publication No. 2008-240123 [Disclosure ofthe Invention] [Problem that the invention is to solve] [0006] An object of an embodiment ofthe present invention is to solve the problems of the related art as described above, and to provide a hot-dip galvanized steel sheet having high strength and improved formability and a manufacturing method thereof. [Means for solving the Problems] [0007] The inventors eagerly reviewed a hot-dip galvanized high strength steel sheet having improved formability. [0008] As a result, with respect to a steel sheet which is a DP (Dual Phase) steel having relatively low yield stress in high strength steel sheets and becomes a substrate of a hot-dip galvanized steel sheet, by controlling a total amount of a Si and a AI, which are components ofthe steel sheet, to a specific range and by controlling a hardness distribution ofthe steel sheet, the inventors found that a hot-dip galvanized high strength steel sheet is capable of obtaining more formability than the related art could be industrially manufactured. [0009] In order to prevent problems such as a delayed fracture or secondary working embrittlement, it is preferable that the steel sheet be a DP steel which substantially - 3 - does not include a residual austenite except for the residual austenite ofapproximately 5% by volume which is inevitably included. Moreover, in the surface portion ofthe steel sheet and the center portion ofthe steel sheet, it is important to control the hardness ofthe martensite or the precipitation state of the MnS in the steel sheet. The aspect of the present invention may be applied to a hot-dip galvanized high strength steel sheet having a tensile strength of 590 MPa to 1500 MPa. However, remarkable effects are exerted on the hot-dip galvanized high strength steel sheet having the tensile strength of approximately 980 MPa. [0010] The gist of the present invention is as follows. [0011] (1) According to an embodiment ofthe present invention, there is provided a hot-dip galvanized steel sheet including: a steel sheet; and a hot-dip galvanized layer arranged on the steel sheet, wherein a component ofthe steel sheet includes, by mass%, C: 0.05% to 0.13%, Si: 0.2% to 0.8%, Mn: 1.5% to 3.1%, P: 0.001% to 0.06%, S: 0.001% to 0.01%, N: 0.0005% to 0.01%, and AI: 0.1% to 0.7%, wherein the balance consisting of Fe and unavoidable impurities, wherein a Si content and an Al content by mass% satisfy the following Equation A, wherein a metallographic structure ofthe steel sheet includes a ferrite and a martensite, and wherein the metallographic structure satisfies the following Equation B when the number of a MnS per 0.1 mrrr' on a surface portion ofthe steel sheet which is a region of 1/8 to 2/8 in a sheet thickness direction is ni, an average equivalent circle diameter of the MnS on the surface portion ofthe steel sheet is d, Jlm"a hardness of the martensite of the surface portion ofthe steel sheet is HI GPa, the number ofthe MnS per 0.1 mnr' on a center portion ofthe - 4 - • steel sheet which is a region of 3/8 to 5/8 in the sheet thickness direction is n2, an . average equivalent circle diameter ofthe MnS on the center portion ofthe steel sheet is d2 urn, and the hardness ofthe martensite in the center portion ofthe steel sheet is H2 GPa. 0.5