PURPOSE: To secure high safety by providing a function of a lock and a key in a mechanical structure and an ID recognizing ability.

CONSTITUTION: When a key 1 is inserted into a key 2 and rotated, an IC contact point part 4 exposed to the side surface of the key 1 is made contact with an IC contact point reception part 5 built in the key 2 and electrically connected to it. Thereafter, an IC memory part 3 of the key 1 is made electrically made contact with an IC lock control part 6 of the key 2, power source is supplied to the memory part 3 from the control part 6 and it comes to be possible to carry out data read-put and write-in motions through a signal conductor. Next, an IC code is read out from the memory part 3 by the control part 6 in accordance with a demand of a host control part 7, and the result is informed to the host control part 7. Subsequently, the host control part 7 judges whether an ID of the key is effective or not, and if it is effective, unlocks a lock system.