Substrate processing apparatus and substrate processing method

A recovery route returns, to a retaining tank, mixed solution supplied to a substrate processing unit. A discarding route discards the supplied mixed solution to a place other than the retaining tank. A switching controller causes the supplied mixed solution to flow into the discarding route during a time interval until a first time interval has elapsed from a time point when the substrate processing unit starts to supply the mixed solution; causes the supplied mixed solution to flow into the recovery route during a time interval until a second time interval, which is decided based on a predetermined recovery rate, has elapsed after the first time interval elapses; and causes the supplied mixed solution to flow into the discarding route during a time interval until supply of the mixed solution has been ended from a time point when the second time interval elapses.