A system for performing a coating and developing treatment for a substrate. The system includes a processing zone having a coating treatment unit, a developing treatment unit, and a heat treatment unit. An interface section carries the substrate between the processing zone and an aligner not included in the system for performing an exposure processing for the substrate. A unit measures the density of impurities at least inside the processing zone or the interface section, and a reduced-pressure impurity removing unit has a chamber which can be closed airtightly for reducing the pressure inside the chamber to a predetermined pressure before the substrate undergoes the exposure processing to remove the impurities adhering to the coating layer on the substrate inside the chamber for a predetermined time. A reduced-pressure control unit controls at least the predetermined pressure or predetermined time based on the value measured by the density measuring unit.