PURPOSE: To make a stepping motor rotatable even under the maximum load of its driving system by providing a driving current controlling means which changes the driving current of the stepping motor in accordance with the load variation of the driving system.

CONSTITUTION: A switching circuit 7 changes the driving current of a stepping motor 3 by selectively switching resistances R1 and R2 which are inserted between a drive circuit 6 and earth and have different resistance values. The motor 3 is rotated in steps when the windings A-D of each phase of the motor 3 are selectively switched in accordance with excitation signals A-D by means of the drive circuit 6 and the driving current I of the motor flows through the circuit 6 and resistances R1 and R2. A detected voltage Vs obtained by converting the driving current I by means of the resistances R1 and R2 is inputted to a differential amplifier 9 and compared with a reference voltage Vr. The degree of conduction of a transistor TR is controlled by means of an output corresponding to the difference.