PROBLEM TO BE SOLVED: To provide a method for producing blood products which can suppress the generation of the fluctuation in the boundary of blood after centrifugal separation, and achieve the sufficiently high acquisition quantities of the separated respective components.SOLUTION: The method for producing blood products uses a blood treatment system including: a storage bag； an almost rectangular filter having a length Xin the horizontal direction and a length Yin the longitudinal direction； a plurality of recovery bags； and a plurality of tubes connecting them. The method includes: a step (A) of charging the blood treatment system inside a centrifugal cup with a depth Yprovided in a centrifugal separator； a step (B) of separating blood into a plurality components by the centrifugal separator； a step (C) of filtering one or two or more components among the two or more components with a filter； and a step (D) of recovering the first specific component(s) which has been subjected to the filtering with the filter, and the sizes of the filter and centrifugal cup satisfy specific conditions.
