A blood bag system (10a) includes a BC pooling bag (54) for centrifugation of a buffy coat, a filter (56) for removing white blood cells from a supernatant liquid transferred from the BC pooling bag (54), a platelet preserving bag (58) for reserving the supernatant liquid that has passed through the filter (56), a first tube (60) connecting the BC pooling bag (54) and an inlet (56a) of the filter (56), a second tube (62) connecting the platelet preserving bag (58) and an outlet (56b) of the filter (56), and a cassette (50a) to be fixed in the centrifugation and separation apparatus. The first tube (60) and the second tube (62) are disposed within the cassette (50a). The cassette (50a) includes a first clamp section (106) for closing and opening the first tube (60), and a second clamp section (108) for closing and opening the second tube (62).
