When a fuel tank is inclined at a negative slope and tilted to the right side, it may be tilted such that a position of a mesh member is relatively higher than a position of a vapor outlet of a vapor outlet passage. In this case, air may enter into a leak passage from an outlet port such that interfacial tension is generated in the mesh member. The interface between fuel and air is present at the mesh member, and the interfacial tension generated at the interface serves to prevent air from entering into a discharge pipe.