A vane pump in which oil is drawn from at least one side, in an axial direction, of a cam ring and is discharged from at least the one side, in the axial direction, of the cam ring, the vane pump including: a portion defined by a groove formed on an inner circumference surface of the cam ring, the groove extending along a circumferential direction of the inner circumference surface and arranged in a position including a middle of an axial direction width on the inner circumference surface in an oil suction section or an oil discharge section of the cam ring, the groove being formed so that a depth of the groove is constantly shallower from a mid-point, in the circumferential direction, of the groove to both ends of the groove.