A valve body and a float body are coupled so that the valve body is allowed to move in a direction along a central axis of movement of the float body, and the seated valve body is unseated when the float body descends. On a central axis side of the movement of the float body, a pair of guide members is provided, and when the valve body tilts, the valve body and the float body contact each other on a lower side of a tilt of the valve body and the float body ascends, so that the guide members correct the tilt. Also, when the float body ascends, the float body and the valve body do not contact each other in a rest of a portion.