To provide an exhaust valve capable of opening a valve port having a large opening area from low pressure to high pressure.

An inlet 4, a valve chamber 3, and an outlet 11 are formed by a casing composed of a main body 1, a bottom lid 2, and a valve seat member 9. An upper valve port 12 and a lower valve port 13 on the same vertical shaft making the valve chamber 3 communicate with the outlet 11 are provided on the valve seat member 9. An opening area of the upper valve port 12 is formed to be slightly smaller than an opening area of the lower valve port 13. A lower valve element 21 for opening and closing the lower valve port 13 is arranged in the valve chamber 3 below the lower valve port 12, and an upper valve element 15 for opening and closing the upper valve port 12 is connected with the lower valve element 21 and arranged on the outlet 11 side between the upper valve port 12 and the lower valve port 13. A guide bar 22 is integrally formed on the lower face of the lower valve element 21, and a float 14 is connected with the lower end of the guide bar 22. The lower valve port 13 is opened and closed by the lower valve element 21 by floating up and lowering the float 14, and the upper valve port 12 is opened and closed by the upper valve element 15.