PURPOSE: To allow a moving body to attain to a prescribed speed within a prescribed time or at a desired position by controlling the moving body with a speed signal until the moving body attains to the prescribed speed, and changing control modes by a phase comparison between the speed signal and a reference signal after the moving body attains to the prescribed speed.

CONSTITUTION: A motor 21 is supplied with maximum power between a start position (a) and a point (c), and the output B of an integrator 43 drops below the reference level (p) of a comparator 44 during the period. The comparison output of the comparator 44 is inverted to a level H at the point (c) and a changeover switch 40 is switched to the side of an amplifier 28'. The gain of the amplifier 28' is smaller than that of an amplifier 28, so the motor input drops as shown between points (c) and (d). When the rotation frequency ff of the motor 21 reaches a reference frequency fr, the integral output falls to the level L and causes the inversion of an inverter 42 to turn on a Tr45, so the output of the comparator 44 falls to the level L to switch the switch 40 to the amplifier 28 again. The switching point coincides with the point (d). A phase comparator 25 detects an error in frequency ff and performs speed control after the rotation attains to the reference speed.