PURPOSE: To provide a flow control valve simple to construct and operate and free of the difference from the contour of an existing double displacement valve.

CONSTITUTION: A flow control valve includes an inner cavity 60 formed in a valve mainbody and an inlet passage 68 and an outlet passage 64 communicating thereto. An actuator is provided with a portion of a rotating shaft 76 located in the inner cavity. A flow control plug member 104 is arranged with a first portion located in the inlet passage and a second portion located in the inner cavity. The first portion has guide structures 106-112 engaged with the wall of the passage for guiding the plug member to the axial direction. The second portion is connected to an actuator shaft 76. The second portion of the plug member and the actuator shaft 76 are connected to each other, so that the rotation of the actuator shaft can be converted into longitudinal motion in the passage of the plug member. A flow control structure 114 is provided in the plug member for controlling the flow out of the valve, with the change of the relative position of the plug in the passage of the plug member.