In a vane pump, a communication groove that provides communication between a communication hole and a discharge port is formed in an outer side face of a rear housing. An opening of the communication groove is blocked by a fitting face of a control valve case. A back-pressure introduction passage that provides communication between the communication hole and an outlet is formed by the communication groove and the fitting face of the control valve case. The back-pressure introduction passage is formed between the rear housing and the control valve case, that is, on the outer side of the housing.