1. A morphing method of a structure shape using a computer, comprising: a preparation step of acquiring at least outer shape information of a structure to be analyzed, and a FEM model, which is generated in advance using a pre-processor of an analysis solver on the basis of a finite element method (FEM), and includes a three-dimensional mesh model that represents an outer shape of a prototype structure and additional information associated with the mesh model, and setting a plurality of corresponding reference points on the outer shape information of the structure to be analyzed and the mesh model of the prototype structure; and a morphing step of calculating a FEM model of the structure to be analyzed by moving a plurality of nodes which form the mesh model of the prototype structure on the basis of correspondence between the plurality of reference points set on the mesh model of the prototype structure and the outer shape information of the structure to be analyzed, so as to change the mesh model to an outer shape of the structure to be analyzed, and merging the additional information and associated state thereof with respect to the deformed mesh model.