Provided is a blood component separation device that can shorten the overall time to collect high-concentration platelet liquid for blood component donation, thereby reducing time to keep a donor for blood drawing. The blood component separation device includes a temporary storage bag (also used as a buffy coat bag) which is also used as a whole blood bag for storing whole blood drawn from the donor. A control means performs whole blood drawing from the donor in parallel with performing at least either of a circulation flow step and an acceleration step, thereby storing the collected whole blood in the temporary storage bag.