To provide an air valve capable of being miniaturized by setting small axial dimensions without decreasing the function of exhausting a large amount of air under pressure and the function of sucking air, and capable of also of preventing water from splashing outside of a valve casing through a large vent hole even if the level of the water rises abruptly before filling of the water and closure.

A float valve element 9 formed in the shape of an upwardly open cup is vertically movably enclosed within the valve casing 2 mounted in communication with a water pipe 1. The large vent hole 6 and a small vent hole 7 are provided in the ceiling 10 of the valve casing 2 to face the interior of the float valve element 9 and the float valve element 9 is provided with a first valve element seat portion 16 moved toward and away from the large vent hole 6 by the rise and fall of the float valve element 9 to open and close the large vent hole 6 and a second valve element seat portion 17 for opening and closing the small vent hole 7.