FUEL TANK CAP LOCKING DEVICE

A fuel tank cap locking device includes: a cap configured to open and close a fuel filler port; an operation unit; an engagement unit movable in conjunction with the operation unit; and a lock unit configured to lock movement of the engagement unit from the engagement position to the allowable position. The lock unit includes a lock member that is movable between an interference position where the lock member interferes with an interfered portion formed at a predetermined position of the engagement unit and locks, and a non-interference position where the lock member does not interfere with the interfered portion and the lock is released when the engagement unit moves from the engagement position to the allowable position by the swing operation of the operation unit.