To provide an air valve which can isolate the inside of a valve box from the inside of a pipe line by letting them be pressed vertically into contact with each other, and is provided with an auxiliary valve structure capable of more accurately isolating the inside of the valve box from the inside of the pipe line.

This air valve is provided with a valve box 10 housing a floating valve body 1, an outer cylinder 20 forming a fluid flowing path in a space interspaced from the valve box 10, and with a valve body part 30 at the upper part of the valve box, a screw shaft 14 is projected out of the valve box 10, which penetrates through a through hole 23 provided for the bottom part of the outer cylinder 20, a sealing member 50 capable of abutting against the lower surface of the outer cylinder, is threadedly engaged with the screw shaft 14, concurrently, a retaining member 26 for the sealing member 50 is provided for the outer cylinder 20, and it is so constituted that let the sealing member 50 abut against the lower surface of the outer cylinder so as to allow the inside of the valve box to be isolated from the inside of a pipe line when the valve box 10 is rotated so as to allow the sealing member 50 to be moved up.