A device (1) for collecting blood in an extracorporeal circuit comprising a venous blood reservoir (2) and a cardiotomy reservoir (3), which are interconnected and provided with couplings (4, 5) respectively to at least one line for conveying venous blood from the patient and to a line for conveying blood collected from the operating field. The venous blood reservoir (2) is provided with a connector (6) for the outflow of the blood toward additional apparatuses comprised within the extracorporeal circuit. The venous blood reservoir (2) and the cardiotomy reservoir (3) are connected to respective independent lines (8, 9) that reach vacuum sources and have, at least as regards the line (9) related to the cardiotomy reservoir (3), a connection (9a) to the atmosphere that has removable blocking means (9b). The vacuum sources are adapted to determine different degrees of vacuum in the apparatuses, the degree of vacuum related the cardiotomy reservoir being higher than the degree of vacuum related to the venous blood reservoir (2). Means are provided for the mutual connection of the venous blood reservoir (2) and the cardiotomy reservoir (3), which comprise a first duct (10) that is connected at its ends to the apparatuses at the bottom and is provided with removable blocking means (12) and a second duct (11) that is provided with removable blocking means (11a), which is connected at one end to an upper lid (2b) of the venous blood reservoir (2) and leads at the other end proximate to the bottom of the cardiotomy reservoir (3).
