PURPOSE: To easily prepare a program for working plural identical shapes on the same circumference.

CONSTITUTION: A working program for a working shape to be worked on a certain position is previously stored. A 1st representative point P1 to be the center position of rotation on a working face and 2nd and 3rd representative points P2, P3 on the working face are set up. Then a rotational angle θ and rotational frequency N are set up (S2). A transformation matrix to be obtained when a working position is successively rotated only by the rotational angle θis prepared (S6). Thus a working program corresponding to each position can be prepared only by specifying the rotary axis and the rotational angle θ.