A control valve (50) controls the displacement of a variable displacement type compressor. The compressor includes a crank chamber (5), suction chamber (21), a bleed passage (27), and a supply passage (28). The control valve has a supply side valve (V2), a transmission rod (80), and a relief side valve (V1). The transmission rod (80) connects the relief side valve (V1) with the supply side valve (V2). The relief side valve (V1) includes a passage chamber (53) constituting part of the bleed passage (27). The passage chamber (53) is separated into a first area (53a), which is connected to the crank chamber (5), and a lower area (53b), which is connected to the suction chamber (21). A pressure sensing member (60) moves the relief side valve body (61) in accordance with the pressure in the upper area (53a). The effective pressure receiving area (A) of the sensing member (60) is substantially equal to the cross sectional area (B) of the passage chamber (53) that is sealed by Lhe relief side valve body (61).