The present invention relates to an apparatus for a pressure-based detection of a clot in an extracorporeal blood circuit, wherein the apparatus comprises at least one cyclically operating pump for conveying the fluid located in the extracorporeal circuit and at least one pressure sensor which is arranged to determine the current pressure development over time in the fluid conveyed by the pump in a current conveying cycle of the pump, wherein the apparatus has at least one memory in which at least one reference pressure development is stored which is based on at least one pressure development over time which was determined in a conveying cycle of the pump preceding the current conveying cycle of the pump, and wherein the apparatus comprises at least one evaluation unit which is configured such that it compares the current pressure development with the reference pressure development over a corresponding time.
