The invention relates to a device for removing the growth on a ship's hull (2). This device comprises a cleaning element (3) and means for displacing this cleaning element over the hull (2), which means comprise at least one cable (4) which is arranged such that it passes underneath the keel of the hull (2) and to which the cleaning element (3) and means (5) for moving the cable (4) are connected. The cleaning element comprises at least one mat (3) comprising a flat base (13) consisting of an elastically deformable material, which at least at one side, is provided with a relief (14) of wear-and-tear-resistant, elastically deformable material. In the mat (3) at least one magnet (17) is provided.