In order to enable tapping to be performed precisely and with an appropriate machining time irrespective of the diameter of a tapping tool, a configuration of the present invention includes: a program analysis unit (12) that analyzes a loaded machining program and extracts thread-related information in tapping; a gradient determination unit (14) that determines acceleration regarding movement velocity of the main spindle or the feed shaft on the basis of the thread-related information obtained by the program analysis unit (12); and an interpolation and acceleration/deceleration processing unit (13) that generates a movement command for the main spindle and the feed shaft using the acceleration determined by the gradient determination unit (14). In addition, the gradient determination unit (14) varies the acceleration during acceleration/deceleration of the main spindle or the feed shaft in accordance with the diameter of a tapping tool.