PURPOSE: To prevent a tool set on a machine tool from giving a return mark to the machining surface of a work or roughening the machined surface by allowing the tool to return on the track, which was offset in the normal direction from the machining surface of the work, when the setting is in the emergency return mode.

CONSTITUTION: When an emergency return switch 10 is turned on, the teach data 11 is input, and on the basis thereof a calculating part 16 calculates the opposite track to the tool track at its time of machining, while another calculating part 17 calculates the normal direction of the machining surface of the work. On the basis of the results from calculations a calculating part 18 calculates the offset track, and the tool is returned to the point of origin along this offset track. This avoids giving a return mark to the normal surface of the work or roughing its surface already machined.