To smoothly operate a main shaft controller in a desired rotational direction even after marker detection without using a special device in the main shaft controller.

The main shaft controller includes: a starting current slow-up processing part 3; a stationary control current operation part 6; and a starting current/stationary control current superposition operation part 16. In the starting current/stationary control current superposition operation part 16, a starting current value is added by making the value constant or small according to the passage of time, the stationary control current value is added by making it large according to the passage of time to be considered as a superposition current instruction value. To a current control part 11, the starting current value is output until a marker signal is output, the superposition current value is output until the marker signal is output and a setting transition period elapses, and the stationary control current is output after the setting transition period by a function of a current instruction switching part 9.