PURPOSE: To enable cancellation of a locked state by a simple construction wherein a worm gear shaft driving an automatic mechanism for setting a cassette tape and a motor shaft are coupled with a play provided.

CONSTITUTION: The shaft of a worm gear 6 driving an automatic mechanism for setting a cassette tape and the shaft of a motor 5 are coupled with a play provided by a coupler 7, and when an excessive torque is given to the gear 6, the gear 6 is moved and locked. When the motor 5 is rotated reversely, the gear 6 is moved in the reverse direction and this locking is canceled. Thus, a locked state of the automatic mechanism for setting the tape is canceled by a simple construction making a complicated clutch and others unnecessary.