PURPOSE: To improve the workability by assembling a master model to a frame body which has formed a wrinkle holding surface on the surface, using it for molding of a copying model, and executing in parallel both working of the frame body and a preparation of the master model.

CONSTITUTION: A wrinkle holding surface 3 is formed on the surface of a frame body 1 made of foam polystylene by a numerical control working device 2. In such a case, as for the frame body, that which has conformed with a size and a shape of a master model 4 is used. Subsequently, the master model 4 is held at a prescribed position by jacks 5, 6, the frame body 1 is assembled exactly, and a mold surface 7 and the wrinkle holding surface 3 are connected as one body. In such a state, plaster is injected onto the mold surface 7 and solidified, consequently, a copying model 9 is molded.