PURPOSE: To perform continuous control over a flow rate while preventing working liquid from leaking when a flow rate control valve is closed.

CONSTITUTION: A piston 12 which axially slides is stored in a housing 11 provided with a 1st port 13 and a 2nd port 16, and energized by an electric magnet 20. A 1st opening and closing valve 14 which has a valve seat part 14C which is open to a 1st liquid chamber A opposite one end part of the piston 12 and a valve body 14B seated on or separated from the valve seat part associatively with the axial displacement of the piston 12 and links and disconnects the 1st port 13 and 1st liquid chamber A is provided between the 1st port 13 and 1st liquid chamber A. An orifice 15 is provided in the communication passage linking the 1st liquid chamber A and 2nd liquid chamber B.