To provide an electric supply plug lock device capable of simplifying a structure of a lock mechanism.

A key cylinder 50 is provided to an inlet for charging. When the key cylinder 50 is operated to rotate to a lock position by a mechanical key, a bar pressing part 66 formed on a back face of the key cylinder 50 presses a lock bar 44 against a energization force of an energizing member 46 from the back. Accordingly, the lock bar 44 moves straight to the left side of the figure, and a thinned portion 48 of the lock bar 44 is positioned at a concave part 42, and a lock mechanism 43 is brought into an unlock condition. When the key cylinder 50 is operated to rotate to the lock position, the bar pressing part 66 is separated and the lock bar 44 moves straight to the right side of the figure by the energization member 46. Accordingly, a movement restraining part 49 is positioned at the concave part 42 and a pawl part of a lock arm is pressed from above, and the lock mechanism 43 is brought into a lock condition.