The present invention concerns a dosing pump comprising a dosing chamber, a working chamber and a dosing diaphragm, wherein the dosing chamber and the working chamber are separated from each other by the dosing diaphragm, wherein there is provided a device for reciprocating movement of the dosing diaphragm between a first position and a second position, wherein the volume of the dosing chamber is smaller in the first position than in the second position. To provide a dosing pump, the dosing diaphragm of which has an increased service life and which as far as possible can be hydraulically operated even at very low dosing fluid pressures at the suction side it is proposed according to the invention that there is provided a prestressing device which prestresses the dosing diaphragm in the direction of the first or second position.