To enable an upper valve element to perform stable lifting operation to a float by performing stable valve closing operation by large buoyancy, in a constitution of the float of a two-stage structure in a fuel cutoff valve.

The fuel cutoff valve 10 has a casing 20 and a float mechanism 50. The float mechanism 50 has the float 51 and the upper valve element 60 liftable to an upper part of the float 51. The float 51 has a valve forming member 54 for dividing a storage chamber 51S into a plurality of pieces. An upper part of the valve part forming member 54 has a storage part 55 having a sub-valve 55d and forming a spring chamber 55S and a partition wall 56 for partitioning a space of an outer wall of the storage part 55 and an inner wall of an upper wall 52 and a sidewall 53. The partition wall 56 is partitioned into an air chamber 56Sa closed in an upper part and a communicating chamber 56Sb opened in an upper part via a claw inserting cutout 56a formed adjacent to an engaging part 52b.