LOCKABLE CAP FOR FUEL TANK

A lockable cap for a fuel tank. The cap (11, 11B, 11C, 11D, 11E) is provided with a ring stopper (26) for making connection and disconnection between an outer cap (21) and a housing cap (23). The ring stopper releases connection between the housing cap and the outer cap upon completion of closing of a fuel filling opening (14), and this ensures that a user does not inadvertently forget to close the cap.