A control valve used for a variable displacement type compressor. The compressor has a crank chamber (5), a discharge pressure zone, and a supply passage (28). The supply passage (28) connects the crank chamber (5) to the discharge pressure zone. The control valve is located in the supply passage (28). The control valve has a valve body (41). The valve body (41) adjusts the size of the opening of the supply passage (28) in accordance with the discharge pressure. The valve body (41) is exposed to the pressure of the supply passage (28). The valve body (41) moves in accordance with the discharge pressure such that the displacement is varied to counter changes of the discharge pressure. The direction in which the valve body (41) moves in response to an increase of the discharge is the same as the direction in which the valve body (41) moves when the pressure of the supply passage (28) increases.