To provide an immersion structure of an air valve, featuring the structure of immersing the air valve in a branch pipe erected from a main pipe in order to prevent the freezing of a water in the air valve.

This structure includes a casing 45 having a large air hole valve seat 20 and a small air hole valve seat 4 at the upper part and a cylindrical passage 2 with a window at the side of a bottom 6 for storing a floating valve body 17 and a valve guide 8, a cylindrical cover 44 having a flange 40 to be fixed to a flange 55 at the end of a branch pipe 61 swollen outwardly in an opening at the upper part and erected from a main pipe 60, a hole 41 at the center of a bottom plate 5 and a packing 42 mounted to the inner periphery, above which a female screw 43 is provided, and a container 47 with a window containing a floating valve 46 moving up and down under a hole 41 to open/close the hole 41. A smoothing portion 49 is provided on the outer periphery of the casing 45 so as to be slidable with the packing 42. The cylindrical passage 2 allows the floating valve 46 to be pushed down to open the hole 41.