Apparatus for collecting blood clots in a blood line for supplying or removing blood in a blood treatment unit of an extracorporeal blood treatment apparatus, wherein the apparatus comprises a housing body having a first connection and a second connection, and a screen body for catching the blood clots that is arranged between the two connections in the flow path of the blood, the apparatus for collecting blood clots being designed such that a flow path bypassing the screen body forms in the housing body when blood flows in at the second connection and out at the first connection, and a flow path bypassing the screen body does not form when blood flows in at the first connection and out at the second connection.