To provide a valve seat structure of an air valve with high reliability of pulling out of the valve seat.

This air valve is constituted so as to form a communicating hole 23 communicating into the duct at the bottom part and arrange a rotating valve 31 opening and closing the communicating hole 23 inside a valve seat 22. This case, a counter bore section 23a is formed at the peripheral section of a valve seat 37 having a rubber seat 38 being brought into pressure contact into a rotary valve body 31 on the counter bore section 23a, a hook channel 36 notching in the radial direction on the counter bore section 23a is formed and a plate-like metal ring 39 coupling to the hook channel 36 is fixed on the valve seat 37. In the valve seat 37 received the flow of pressure water, the drag against the flow of the pressure water is acted to surely prevent from pulling out of the valve seat 37 by inserting the metal ring 39 into the hook channel 36 and hooking.