PURPOSE: To perform a small angle rotation easily by inputting an analog reference voltage and an analog value obtained by D/A conversion of a digital signal from a controller to an analog switch and by switching, selecting and converting them into current values.

CONSTITUTION: D/A converter 2 receives an analog reference voltage and a digital signal from a controller 1 and D/A converts them to output an analog output voltage for changing a specified angle of rotation. When the output voltage and reference voltage from the converter 2 is inputted to an analog switch part 3, respective output parts 3-1 to 3-5 of said analog switch part 3 are successively switched according to a command of the controller 1 to operate power amplifiers 4-1 to 4-5 and to excite respective phases (five phases in the drawing) of a stepping motor 5 to step a rotor 7, successively. Thus, a small angle rotation is performed accurately by a simple structure.