An external rotor pump has an outer rotor with a sliding surface which is arranged on the outer side thereof, and an opposing body in which the outer rotor is mounted rotatably by way of the sliding surface thereof on an inner guide surface of the opposing body and is in mechanical contact with the inner guide surface. An inner rotor which is mounted such that it can be rotated eccentrically with respect to the outer rotor is provided. The sliding surface or the inner guide surface has a surface structure which has a load-bearing region and a non-load-bearing region which is depressed in contrast with the former.