To provide a lock of high safety by driving a plurality of gears with a key having a coding bit, turning a plurality of driven gears having a lock blot recess, and releasing the lock with each gear recess kept aligned.

A rotor 43 is formed out of a plurality of gears and each gear is formed to be independently capable of being driven. Furthermore, a plurality of gears 59 having a slot 61 are combined to form a driven element 5, and mounted so as to keep a variable center distance with the rotor 43. On the other band, a coding bit is formed on the end 29 of a key 2. Then, when this key 2 is inserted in a key groove 10 and turned, each gear of the rotor 43 is rotated, together with each gear of the driven element 58. As a result, the slot 61 of each gear 59 is properly positioned and a rock bolt recess 62 is formed, thereby causing a rock bolt 23 to retreat and release a lock. For positioning the slot 61, a dial lock system is applied, and the rotor 43 and the driven element 58 are disengaged from each other wherever necessary for adjustment. According to this construction, a key operated lock of high safety can be provided.