Provided is a blood component separation device and related method, each capable of separating a blood component from blood and rapidly performing a virus inactivation process on the separated blood component. The blood component separation device includes a blood component separation section, provided in a centrifuge, configured to separate a blood component from blood by centrifugation, a diluting section configured to dilute, in a diluent containing riboflavin, concentrated red blood cells separated by the blood component separation section, and a UV light emitting unit configured to perform a virus inactivation process by exposing the concentrated red blood cells thus diluted to the UV light.