PURPOSE: To provide a gremorne lock controlling projecting and retreating of a lock rod by means of a micromotor by forming a push-off tooth at least on one gear in locking a receiving gear and an unlocking receiving gear.

CONSTITUTION: A locking rod 16 is combined with a slider 2 guided movably in the vertical direction in a lock box 1, and the slider 2 is driven by an operating arm 18 rotationally moved by a drive power transmission device from a micromotor 25 to a sector gear 24b. Next a locking lever 21 is engaged with a locking step part 19 formed on the slider 2 and locking is released by an unlocking lever 22 at descent of the slider 2. Next changeover of locking and unlocking is carried out by connecting a planet gear 31 to either of fine adjusted gear trains for locking/unlocking 37,38 while utilizing swing of a differential gear 32. The face width of tooth painted out into black of a receiving gear 33,34 for locking or unlocking is made larger than the other teeth so as to make a push-off tooth 39, and at completing the operation for locking or unlocking a swing arm 29 is pushingly moved by the tooth 39 so as to intercept torque from the motor 25.