A variable displacement pump comprising: a rotor that is driven and rotates; a plurality of vanes that are provided at an outer circumferential portion of the rotor so as to be able to extend and retract; a ring-shaped movable member that defines a plurality of working fluid chambers by accommodating the rotor and the plurality of vanes at an inner circumferential side of the movable member and changes a volume variation of each working fluid chamber during rotation of the rotor by moving so that an inner circumferential center of the movable member changes with respect to a rotation center of the rotor; a pump housing that houses therein the rotor, the vanes and the movable member, both axial direction end surfaces (5h, 5i) of the movable member being in sliding-contact with both opposing inside surfaces of the pump housing; an inlet section (11a, 11a') that is formed on at least one of the both inside surfaces of the pump housing and opens in an inlet-side area where a volume of each working fluid chamber is increased by the rotation of the rotor; an outlet section (12a, 12a') that is formed on at least one of the both inside surfaces of the pump housing and opens in an outlet-side area where the volume of each working fluid chamber is decreased by the rotation of the rotor; a first control hydraulic chamber that, by an internal pressure thereof generated by being supplied with a discharge pressure discharged from the outlet section (12a, 12a'), gives a force to the movable member in a direction in which the volume variation of each working fluid chamber is decreased; a second control hydraulic chamber that, by supply and discharge of the discharge pressure and interruption of the supply of the discharge pressure which are selectively switched by a switching mechanism, gives a force to the movable member in a direction in which the volume variation of each working fluid chamber is increased; a first seal part that is formed on the both end surfaces (5h, 5i) of the movable member, which are in sliding-contact with the both inside surfaces of the pump housing, and seals a gap between each working fluid chamber and the first control hydraulic chamber; and a second seal part which is formed on the both end surfaces (5h, 5i) of the movable member and seals a gap between each working fluid chamber and the second control hydraulic chamber in the outlet-side area, characterized in that a radial direction width of the second seal part throughout the outlet-side area, except a vicinity of a pivot portion and a vicinity of a seal member which define the second seal part, is greater than a radial direction width of the first seal part. a rotor that is driven and rotates; a plurality of vanes that are provided at an outer circumferential portion of the rotor so as to be able to extend and retract; a ring-shaped movable member that defines a plurality of working fluid chambers by accommodating the rotor and the plurality of vanes at an inner circumferential side of the movable member and changes a volume variation of each working fluid chamber during rotation of the rotor by moving so that an inner circumferential center of the movable member changes with respect to a rotation center of the rotor; a pump housing that houses therein the rotor, the vanes and the movable member, both axial direction end surfaces (5h, 5i) of the movable member being in sliding-contact with both opposing inside surfaces of the pump housing; an inlet section (11a, 11a') that is formed on at least one of the both inside surfaces of the pump housing and opens in an inlet-side area where a volume of each working fluid chamber is increased by the rotation of the rotor; an outlet section (12a, 12a') that is formed on at least one of the both inside surfaces of the pump housing and opens in an outlet-side area where the volume of each working fluid chamber is decreased by the rotation of the rotor; a first control hydraulic chamber that, by an internal pressure thereof generated by being supplied with a discharge pressure discharged from the outlet section (12a, 12a'), gives a force to the movable member in a direction in which the volume variation of each working fluid chamber is decreased; a second control hydraulic chamber that, by supply and discharge of the discharge pressure and interruption of the supply of the discharge pressure which are selectively switched by a switching mechanism, gives a force to the movable member in a direction in which the volume variation of each working fluid chamber is increased; a first seal part that is formed on the both end surfaces (5h, 5i) of the movable member, which are in sliding-contact with the both inside surfaces of the pump housing, and seals a gap between each working fluid chamber and the first control hydraulic chamber; and a second seal part which is formed on the both end surfaces (5h, 5i) of the movable member and seals a gap between each working fluid chamber and the second control hydraulic chamber in the outlet-side area, characterized in that a radial direction width of the second seal part throughout the outlet-side area, except a vicinity of a pivot portion and a vicinity of a seal member which define the second seal part, is greater than a radial direction width of the first seal part.