To provide an air valve capable of preventing closing impossible of a large air hole generated by biting of foreign matter between a floating valve element and a valve seat and saving space.

The large air hole 6 is formed at an upper end part of a valve box 2. A communication hole 5 communicated with the inside of a flow conduit is formed at a lower end part of the valve box 2. At the inside of the valve box 2, the floating valve element 7 to open/close the large air hole 6, a float 8 to elevate/lower the floating valve element 7, and a cylindrical guide frame body 9 to guide the floating valve element 7 and the float 8 in an elevating/lowering direction are provided. A flow hole 10 opened to inside and outside faces is formed on a side part of the guide frame body 9. When the floating valve element 7 rises and is abutted on the valve seat 13 formed around the large air hole 6, the large air hole 6 is closed by the floating valve element 7. A strainer 18 for removing foreign matter included in water flowing in a flow passage 17 leading from the communication hole 5 to the flow hole 10 is provided between an inner peripheral surface of the valve box 2 and an outer peripheral surface of the guide frame body 9.