To inject air without using injecting needle by fitting a cylindrical rubber valve provided with a hole for injecting air in a center part and a longitudinal direction slit into a hole which is pierced in the center part of fastening rubber, projecting a valve tip part from the fastening rubber hole and forming an air supply valve.

An air injecting hole 3 is provided in a center part on an upper surface, and further, a longitudinal direction slit 4 which reaches the lower surface of a cylinder successively from the hole 3 is provided in a cylindrical valve 2. The valve 2 is fitted to a hole 7 provided in fastening rubber 6 against the elasticity of the rubber 6. Then, a projecting part 5 of the vale 2 which is projected from the fastening rubber 6 is fitted to a hole 10 which is piercingly provided in a material 9 of a ball 8 and adhered to the inner surface of the material 9 of the ball 8 by a rubber adhesive 11 so that an air supply valve 1 is constituted. In this case, the inner diameter B of the hole 7 provided in the fastening rubber 6 and the outer diameter A of the valve 2 are set to become a relation of 0.3≤B/A≤0.8 so that an air leakage at the time of putting in/out an air injector 18, when the air is injected into the ball 8, is surely prevented.