A charging port locking device is provided that basically includes a charging port and a lock mechanism. The lock mechanism achieves both locked and unlocked states by rotational movement of the restricting member. The restricting member is configured in the lock state with respect a reference line connecting a center of rotation of the restricting member and the center of width of the engaging portion as seen in a top view such that a top view area of the restricting member from the reference line in the rotational direction toward a restricting state is smaller than a top view area of the restricting member from the reference line in the rotational direction toward a non-restricting state.