A valve rod is accommodated in a valve chest which is in communication with a plurality of ports, the valve rod has a round poppet valve disposed between a supply valve seat and a discharge valve seat, an annular protruding wall is formed on a side surface of the poppet valve, the protruding wall has a circumference surface including a cylindrical surface extending in parallel with an axial line of the valve chest and an inclined surface which enables the base end of the cylindrical surface to be smoothly continuous with the side surface of the poppet valve, and the cylindrical surface has a diameter smaller than that of the poppet valve and larger than that of a narrow portion of the valve rod.