To easily form a lock device of the return type including a coin- detecting mechanism of a locker for rent which can be locked by means of a key by putting coins into the lock device.

The locking device 1 comprises a casing, a coin feed port 3, a coin detecting mechanism 4 for selecting coins fed through the port 3 depending on the outer configuration thereof, a locking rod 6 for engaging and disengaging a striker, a drive device 8 for moving the rod 6 by means of a key, and a coin return port 9. In this case, a coin selecting piece 10 which can be positioned according to the configuration of coin, an engaging piece 11 which is engaged with the rod 6 before a coin is fed and which is rotated when a coin is fed and disengaged from the rod 6, a first holder part 6a formed integrally to the rod 6, and a second holder part 6d are provided, and a first holder means is formed of the piece 10, piece 11, and first holder part 6a, and a second holder means is formed of the part 6d and an engaging piece 17 formed integrally to the casing.