A biological component collection system and a circuit internal pressure acquisition method are provided, which are capable of accurately measuring the circuit internal pressure. A centrifugal separation device of a blood component collection system comprises an estimated data calculation unit that calculates estimated data B on the basis of initial data A, and a correction unit that corrects the estimated data B in a manner so that the internal pressure calculated by a first internal pressure calculation unit becomes equivalent to the internal pressure calculated by a second internal pressure calculation unit.