To provide a lock device of a cover which is not moved by an unrelated third party.

The lock device is operated by inserting a wrench (3) into an opening (4) at the cover (1). The wrench (3) has an identification code storage means (40). When the wrench (3) is inserted into the opening (4), an identification code is read by an identification code reading means (41) integrated with the cover (1) and is compared with an identification code which is preliminarily stored in an electronic module (44) integrated with the cover (1). When the identification code read by the identification code reading means (41) does not coincide with the identification code which is preliminarily stored in the electronic module (44), the operation of lock (6) is not carried out by an operation disturbing member (46) which makes it unable to operate the cover (1).