[Problem] To provide an extracorporeal circulation apparatus capable of reliably detecting a position of a liquid surface (blood surface) stored in a blood reservoir.[Means for Resolution] An extracorporeal circulation apparatus 2 includes a blood reservoir 3 in which blood is temporarily stored, a presence information acquisition unit 9 that acquires pieces of presence information on blood 21 stored in the blood reservoir 3, and a control unit 7 that executes control to determine the position of a blood surface 22 on the basis of presence or absence of consecutiveness between pieces of the presence information acquired along at least one of a first direction parallel to the blood surface 22 of the blood 21 stored in the blood reservoir 3 and a second direction perpendicular to the blood surface 22 among pieces of the presence information transmitted from the presence information acquisition unit 9.
