To provide a float which can prevent generation of hunting and water hammering even if a minute variation of a water level is frequently repeated by waving of a water surface when a valve body is held in a fully closed state or a small opening state.

Even if a float 9 quickly rises after falling once to close a valve body 2 due to minute variation of a water level is frequently repeated by waving of a water surface of a water tank 5 when the valve body 2 in a valve casing 1 is held in a fully closed state, or even if the float 9 quickly rises to close the valve body 2 due to minute variation of a water level is frequently repeated by waving of the water surface when the valve body 2 is held in a small opening state, the quick valve closing movement is slowed down by the action of a damping unit 20.