To provide a fuel shut-off valve 10 which has a structure of making an upper valve element 55 easy to attach to a float 51 and hard to detach by the swelling of a fuel.

The fuel shut-off valve 10 includes a casing 20 and a float mechanism 50. The float 51 of the float mechanism 50 has a pressing part 54, which forms an insertion part 54a at its lower part. An upper valve body 56 of the upper valve element 55 comprises a guide member 57, which is formed from the outside circumferential part of the upper plate part 56a and provided protrusively in a cantilever shape in the up/down direction. When the guide member 57 is attached to the float 51 and when the lower part of the guide member 57 is inserted into the insertion part 54a and the guide side engagement parts 57a pass over float side engagement parts 52c, the guide member 57 moves toward the float 51 while bending with the lower part of the guide member 57 restrained by the pressing part 54 from expanding to the outside.