PURPOSE: To ensure the return of a tap in a complete through condition by providing a main spindle rotation command means, a code select means, and an arithmetic means for correcting a tap return amount when the rotation of a main spindle has been changed over toward a tap return direction.

CONSTITUTION: The titled device comprises a central processing means 1 for controlling the whole of the device, a memory means 2 related thereto, a feed drive means 3 for a workpiece table, a main spindle rotation drive means 4 for tapping a main spindle rotation command means 5 for changing over the rotary direction thereof,a code select means 6 for selecting each code from a machining program, using alphabets, and an arithmetic means 7 for spindle rotation command means 5 transmits a reverse rotation instruction to the code select means 6 upon inputting a signal for machining feed finish, and sends a spindle direction changeover signal to the arithmetic means 7, thereby causing a speed instruction to be outputted, correcting a return speed rate and returning a tap completely to an R point.