To prevent water leakage and damage to an elastic member even when water rapidly flows into a valve chamber from an inflow port.

The valve chamber 3 is formed with an inflow port 4 opened in a lower part and an outflow port 5 opened in an upper part. A valve seat 6 is formed between the valve chamber 3 and the outflow port 5. Inside the valve chamber 3, a float receiver 10, which is of approximately a cylindrical shape having a bottom and which has a through-hole 11 communicating the inside and outside of the receiver with each other in the bottom, is arranged with a channel provided between itself and the inner wall of the valve chamber 3. A spherical float 12 is arranged in the float receiver 10 in a free condition. A sidewall 10a and the bottom wall 10b of the float receiver 10 are separately formed. The sidewall 10a is fixed in the valve chamber 3 and the bottom wall 10b is arranged while being biased to the inflow port 4 side by a coil spring 13 as an elastic member. The force of water that rapidly flows from the inflow port 4 into the valve chamber 3 displaces the bottom wall 10b of the float receiver 10 to the outflow port 5 side against the coil spring 13 and makes the float 12 approach the valve seat 6. When the float 12 is floated and seated on the valve seat 6 by the force of water that flows into the float receiver 10, a valve is closed.