To provide an air valve which can immediately discharge almost all of the water blown out during exhaust to the outside and can secure proper operations of a floating valve body by suppressing rusting of the floating valve body and an annular lid, and at the same time, in which work for inspecting water leakage can be easily executed by making troublesome and difficult work to detach a cover unnecessitated.

A radially extended groove-like drainage path 13 is recessed at the peripheral wall part 7A of the annular lid 7. Almost all of the water W accumulated in an annular recess 12, which is formed between the outer peripheral face of the floating valve body 5 and the inner peripheral face of the annular lid 7 during closing of an air hole 9 by the floating valve body 5, is discharged to the outside of a valve casing 2 by the water W blown out during exhaust by the grooved drainage path 13.