<；P>；PROBLEM TO BE SOLVED: To obtain the accurate weight of a bag enclosing the whole blood when separating a plasma layer from the blood separated into a red blood cell layer and the plasma layer and collecting it. <；P>；SOLUTION: The blood separation apparatus comprises: a first bag (11) enclosing the blood separated into the red blood cell layer and the plasma layer； a plurality of second bags (12 and 13) connected through a tube from the first bag (11)； a weighing part (43) for mounting the first bag (11) and performing weighing； a housing chamber (40) for pressurizing the first bag (11) mounted on the weighing part (43) and forcibly feeding the plasma to the tube； a weighing data acquisition means (99) for acquiring the weighing data (m) of the weighing part (43) at a plurality of points of time in a period from the mounting of the first bag (11) on the weighing part (43) to the start of the pressurization； and a weight determination means (101) for determining the weight of the first bag (11) on the basis of the two or more pieces of the acquired weighing data (m). <；P>；COPYRIGHT: (C)2008,JPO&INPIT
