A vane motor comprising: a casing including a fluid inlet and a fluid outlet, through which a pressurized fluid comes in or out; a rotor being installed in the casing, turning around a rotational shaft by the pressurized fluid and including a rotor body which has a substantially cylindrical shape and an axis coinciding with an axis of the rotational shaft and a plurality of vanes which is installed in grooves formed on an outer circumferential surface of the rotor body and has a portion protruding from the groove and (the portion) having a length varied in accordance with a rotational phase, and an inner liner of a cylindrical shape which is installed in the casing and receives the rotor therein, in which a distal end of the vane comes into contact with an inner wall surface of the inner liner while the pressurized fluid is retained therein until the pressurized fluid flowing through the fluid inlet (135, 155) of the casing is discharged from the fluid outlet (133, 153) of the casing, and an imaginary rotational axis of the inner liner is spaced apart from a rotational axis of the rotational shaft in a parallel state, but is able to rotate together with the rotor when the rotor turns, characterized in that the casing is configured in such a way that both ends of an outer liner of a cylindrical shape larger than the inner liner are closed by disc-shaped finish plates (13, 15), there is a fine gap in axial (longitudinal) direction between the finish plates (13, 15) and the inner liner and the vanes, so that the inner liner and the vanes are able to slide with the finish plates (13, 15), but the pressurized fluid is hardly leaked through the gap, at least one of the finish plates (13, 15) is provided with a fluid inlet (135, 155) and a fluid outlet (133, 153), an enlarged portion through which a rear (in respect of rotation direction) surface of the vane is more exposed is formed on at least one (axial) end of a rear (in respect of rotation direction) side edge portion forming the opening of the groove, and wherein the fluid inlet (135, 155) is arc-shaped and, at least at a start portion of the arc-shape, is overlapped with the enlarged portion. a casing including a fluid inlet and a fluid outlet, through which a pressurized fluid comes in or out; a rotor being installed in the casing, turning around a rotational shaft by the pressurized fluid and including a rotor body which has a substantially cylindrical shape and an axis coinciding with an axis of the rotational shaft and a plurality of vanes which is installed in grooves formed on an outer circumferential surface of the rotor body and has a portion protruding from the groove and (the portion) having a length varied in accordance with a rotational phase, and an inner liner of a cylindrical shape which is installed in the casing and receives the rotor therein, in which a distal end of the vane comes into contact with an inner wall surface of the inner liner while the pressurized fluid is retained therein until the pressurized fluid flowing through the fluid inlet (135, 155) of the casing is discharged from the fluid outlet (133, 153) of the casing, and an imaginary rotational axis of the inner liner is spaced apart from a rotational axis of the rotational shaft in a parallel state, but is able to rotate together with the rotor when the rotor turns, characterized in that the casing is configured in such a way that both ends of an outer liner of a cylindrical shape larger than the inner liner are closed by disc-shaped finish plates (13, 15), there is a fine gap in axial (longitudinal) direction between the finish plates (13, 15) and the inner liner and the vanes, so that the inner liner and the vanes are able to slide with the finish plates (13, 15), but the pressurized fluid is hardly leaked through the gap, at least one of the finish plates (13, 15) is provided with a fluid inlet (135, 155) and a fluid outlet (133, 153), an enlarged portion through which a rear (in respect of rotation direction) surface of the vane is more exposed is formed on at least one (axial) end of a rear (in respect of rotation direction) side edge portion forming the opening of the groove, and wherein the fluid inlet (135, 155) is arc-shaped and, at least at a start portion of the arc-shape, is overlapped with the enlarged portion.