To provide a locking device in which the rotational movement of a rotor of a lock is transmitted as the vertical movement of a key plate to a key rod provided along the breadth direction, by changing the direction of the rotational movement 90 degrees using simple constitution, the key plate having almost the same height and the same length on either side of its main body.

In a cylinder lock, an inner cylinder serving as the rotor of the lock rotated by a key is provided with a first bevel gear 3 securely connected thereto by a pin 6, and a second bevel gear 4 meshing with the first bevel gear 3 is provided on a key rod 2; the rotational movement of the rotor of the lock is transmitted via the first and second bevel gears 3, 4 by the normal and reverse rotations of the key in such a way that the direction of the rotational movement of the key rod 2 is changed to an approximately perpendicular direction, so that locking can be achieved. Thus by using the bevel gears 3, 4, the transmission of force becomes constant to allow smooth operation and to prevent the loss of the rotational movement.