1. A method for analysis of shape optimization comprising optimizing a part of a structural body model including a movable portion, by combining a multi-body dynamics analysis and an optimization analysis and using two-dimensional elements or three-dimensional elements, the optimizing includes: a design space setting step of setting, as a design space, a portion to be optimized in the movable portion; an optimization block model generating step of generating, in the set design space, an optimization block model formed of three-dimensional elements and is to be subjected to analysis processing of optimization; a connection processing step of connecting the generated optimization block model with the structural body model including the movable portion; a material property setting step of setting a material property for the optimization block model; an optimization analysis condition setting step of setting an optimization analysis condition to determine an optimum shape of the optimization block model; a multi-body dynamics analysis condition setting step of setting a multi-body dynamics analysis condition including a centrifugal force, a reaction force and an inertial force to perform multi-body dynamics analysis on the structural body model including the movable portion with which the optimization block model has been connected; an optimum shape analyzing step of executing, based on the set multi-body dynamics analysis condition, the multi-body dynamics analysis on the structural body model including the movable portion incorporating the optimization block model; executing, based on the set optimization analysis condition, the optimization analysis; and finding the optimum shape of the optimization block model, and utilizing the analysis of shape optimization for configuring optimization of the movable portion of the structural body configured of a thin sheet; and displaying the structural body model including the moveable portion based on the optimum shape analyzing step; wherein the optimization block model is generated by: setting nodes in a portion connected with the two-dimensional elements or three-dimensional elements forming the structural body model; and stacking the three-dimensional elements along a plane including the nodes set in the connected portion.