The subject matter of the present invention is a variable-delivery pump device comprising a pump body (2), an impeller (5) and a shut-off element (8) capable of translational movement and adjustably covering at least part of the outer periphery of the impeller (5), as well as a cam element (9) which is rotationally driven and engages with said shut-off element (8) for effecting the translational movement thereof. The pump device (1) is characterized in that the shut-off element (8) and the cam element (9) have cylindrical walls (8′) and are arranged concentrically around the housing (7) that accepts the shaft (6) of the impeller (5), and in that the rotary cam element (9) is situated on the inside of the sliding shut-off element (8) and, on the external face of its wall, has at least one helical guideway (11) on which there runs at least one corresponding follower element (12) secured to the internal face of the wall (8′) of the shut-off element (8).