To prevent fuel from flowing out to the outside even if a vehicle rocks or tank inner pressure suddenly rises, in a two stage float structure.

A fuel shut-off valve 10 includes a casing 20 and a float mechanism 50. The float mechanism 50 includes a cup shape float 51, and an upper valve element 55 which is mounted at an upper part of the float 51 in such a manner that the same can move up and down, which opens and closes a connection passage 32a, and which has a connection hole 58c having smaller passage area than that of the connection passage 32a formed therethrough. A through-hole 52b is formed in an up-and-down direction through an upper wall 52 of the float 51. The upper valve element 55 forms a gap 55S for ventilation with a prescribed gap to the upper wall 52 maintained, and forms a shut-off wall 56f at a position opposing to the through-hole 52b.