This valve seat is disposed below a valve ball, wherein the valve seat comprises an annular member in which a seating surface and a lower end surface of the valve ball are formed into a circular shape; a flow path is formed between the seating surface and the lower end surface, for communicating a transfer fluid including a gas and a liquid; and the flow path is formed in a predetermined shape in which a horizontal distance from the central axis which crosses the lower end surface at right angle to the inner circumferential surface of the flow path excluding the seating surface and the lower end surface is not constant over the entire circumference of the flow path.