To provide an exhaust valve having large vacuum break ability and quickly performing vacuum break.

A valve chamber 3 having an inflow port 4 in the lower part and an outflow port 5 in the upper part is formed by a casing comprising a main body 1 and a cover 2. A valve seat 6 is formed between valve chamber 3 and the outflow port 5. The main body 1 integrally has a plurality of rids 9 protruded to an inner side in an inner wall of the valve chamber 3, and a bottomed float receiver 10 almost in cylindrical shape having a through hole 11 of small opening area in a bottom part is fixed by a snap ring in an inner side of the rib 9. A spherical float 12 is arranged in a free condition in the float receiver 10. The float receiver 10 has in its side wall many communication holes 13, and a total opening area of the communication holes 13 is formed in a size making the outside air flowing in the float receiver 10 quickly pass through without retention. The outside air flowing in the float receiver 10, passing through the communication hole 13, is made to easily pass through out of the float receiver 10, so at to reduce the air sprung back by colliding against the bottom part of the float receiver 10, and a pressure under the float 12 in the float receiver 10 is difficult to rise. Consequently, the float 12 prevented from easily floating up.