Abstract: A fuel tank system has a fuel tank, a fuel charging port extending from the fuel tank and disposed in the vicinity of an outer panel of a body and a fuel lid for covering the fuel charging port. The fuel lid is mounted such that it is movable substantially horizontally relative to a portion of the outer panel of the body corresponding to the fuel charging port and that a distal end of the fuel lid is capable of moving away from the fuel charging port and the outer panel. A fuel passage having an outlet disposed on a rear surface side of said fuel lid in such a manner as to be oriented downwardly is disposed in such a manner as to extend from said fuel tank. This fuel passage allows a liquid fuel overflowing during overfueling to flow.