1. A 3-dimensional (3D) model shape transformation method, comprising: generating a volume model, in which a shape of an object is restored, based on a plurality of 2D images of the object; generating a skeleton structure of the volume model using boundary points between portions of a body of the volume model; generating a skeleton transformation model by transforming a skeleton structure of a template model into the skeleton structure of the volume model in order to match a size and a posture of the template model with a size and a posture of the volume model; and generating a shape transformation model corresponding to the shape of the object by transforming appearance of the skeleton transformation model based on cross-sections of the volume model in order to match appearance of the skeleton transformation model with appearance of the volume model.