PURPOSE: To make copying work so accurate by finding an incline of a model surface at time of pick feed starting, and when it is more than the specified value, executing the pick feed with a first plane and when it is less than the specified value, with a second plane, respectively.

CONSTITUTION: Setting a horizontal axis to an X-axis, a vertical axis to a Z-axis and a paper surface vertical axis to a Y-axis, respectively, when a tilt angle with both XY planes of a model 41 is set down to θa, this angle is found out of a vector of composite displacement a to be detected by a stylus 21. When the tilt angle θa is smaller than the specified value, a pick feed plane should be set to Y-Z plane. It means that an X-axis is fixed, the Y-axis is set to the copying direction and the Z-axis to a copying axis, respectively. A model 42 is the case where a tilt angle θb is larger than the specified value, the pick feed surface should be set to the X-Y plane. It means that the Z-axis is fixed thereto, the Y-axis to the copying direction and the X-axis to the copying axis, respectively. With this constitution, even in the case of such a model as altering the surface tilt angle so largely, stable pick feed operation can be performed, thus such copying operation as excellent in accuracy is made possible.