PURPOSE: To change the driving speed of a stepping motor in a wide range by constituting so that the relative position of an output shaft to which a rotor is fitted and a stator surrounding the rotor can be displaced in the direction of the output shaft.

CONSTITUTION: A zoom driving motor 1 and a focus driving motor 22 are constituted of the stepping motor rotating by accurate equal rotation angular motion, and the stator 1d of the motor is constituted to be able to displace in the direction of a lead screw 1f. Namely, a groove hole 1b is made on one side peripheral surface of the main body 1a of the stepping motor, and an almost ring-type attaching frame 1c is movably fitted inside the hole 1b in a state where it can slide. Then, the stator 1d surrounding the rotor 1e through a gap is fitted on the attaching frame 1c, and the rotor 1e is fitted in the lead screw 1f. When the stator 1d surrounding the rotor 1e is displaced in the direction of the output shaft, the opposed area of the stator 1d and the rotor 1e is increased or decreased, so that the generated torque amount of the motor is changed as necessary.