To provide an exhaust valve capable of normally opening/closing by preventing deformation of a float.

A valve chamber 3 with an inlet port 4 opened to a lower part and an outlet port 5 opened to an upper part is formed by a casing comprising a body 1 and a lid 2. A valve seat 6 is formed on a valve chamber 3 side opening end of the outlet port 5. The spherical float is disposed in the valve chamber 3 in a free state. A cross-like retaining part 13 is formed on the outlet port 5 integratedly with the lid 2. The retaining part 13 is partially formed to a spherical shape with its float 12 side lower surface coincident with an outer surface of the float 12. The retaining part receives the float 12 when the valve is closed with the float 12 seated on the valve seat 6. Since the float 12 is received by the retaining part 13, it is not deformed even if it receives impact by water hammer or the like.