Substrate processing system and substrate processing method

The present invention relates to a substrate processing system and a substrate processing method capable of cleaning a processing-liquid supply line. A substrate processing system includes: a substrate processing apparatus (1) configured to process a substrate W; and a flushing device for cleaning a distribution line (93) and a processing-liquid supply line (92). The flushing device includes: a cleaning-liquid supply line (99) coupled to the distribution line (93); a drain mechanism (101) configured to direct a cleaning liquid, supplied into the processing-liquid supply line (92) through the distribution line (93), to a liquid disposal area (100); a supply switching valve (104) configured to allow only the processing liquid or the cleaning liquid to flow in the distribution line (93); and an operation controller (30) configured to control operations of the drain mechanism (101) and the supply switching valve (104).