The invention relates to a diaphragm pump for pumping aggressive and/or abrasive media, such as slurries, comprising a diaphragm housing mounted in a substantially vertically disposed pipe system, which substantially vertically disposed pipe system comprises at least one inlet and at least one outlet positioned some distance above the inlet, as well as at least one substantially circular, flexible diaphragm, which diaphragm is movable within the diaphragm housing under the influence of a working liquid to be pressurised, in which the circular outer edge of the diaphragm is clamped down in the diaphragm housing by means of a circular clamping member. According to the invention, the diaphragm pump is characterized in that the circular clamping member is provided, on the circumferential edge thereof, with a flange that extends parallel to the plane formed by the clamping member. Since the circular clamping member is provided with a flange extending in the plane formed by the clamping member, disadvantageous deformation of the diaphragm during the delivery stroke will be prevented, because the deforming diaphragm will come to abut against the flange.