To remove an undercut part from three-dimensional data of the inner face, the program includes a surface model creating means to create a surface model based on three-dimensional data of a gypsum model including an abutment tooth, a cutting direction specifying means to specify a direction of a cutting bar, and a surface model creating means to create a surface model for machining by changing the three-dimensional data to have new coordinates by determining a base axis in parallel with the cutting bar in the surface model and plane moving coordinates of the cutting bar, and converting the coordinates of a point which becomes an undercut part, to be equal to the plane moving coordinates of a point having a high height from a specified face rectangular to the base axis at the opposite side of the occlusion face and a long distance from the base axis.