To provide a full tank control valve capable of keeping dimension in a height direction of a fuel tank small while maintaining capacity of the fuel tank.

A jet pump 44 is provided as a discharge means for discharging fuel flowing into a housing 31 of a full tank control valve 30. Fuel in the housing 31 is sucked into the fuel tank 10 by a jet pump 44 and the full tank control valve 30 is changed over to a communication state during operation of the engine after the fuel tank 10 is filled. Position of a valve seat 32 of the full tank control valve 30 is arranged at a position lower than a full tank liquid surface position F of the fuel tank 10. Consequently, the dimension in the height direction of the fuel tank 10 including the full tank control valve 30 can be made small.