To provide a lock device capable of preventing the theft of an engaging member.

A power feeding connector 1 as the engaging member has an engaging claw 17 for engaging with a protruded part 20 of a power receiving connector 2. With the engaging claw 17 engaging with the protruded part 20, the power feeding connector 1 is held in the condition of being connected to the power receiving connector 2. When, in linkage with the operation of an operation part 18, the engaging claw 17 is moved to a position to cancel the engagement with the protruded part 20, the power feeding connector 1 can be pulled off. A lock device 4 comprises: a cover member 6 for oscillating to a position to cover the operation part 18 and to a position not to cover the operation part 18 on the basis of the application of outer force; and a mounted member 5 to be mounted on the power feeding connector 1. When the cover member 6 is moved to the position to cover the operation part 18, the cover member 6 is held at that position. When a key cylinder 60 is operated by a mechanical key 61, the holding of the cover member 6 is cancelled.