Provided is a substrate processing apparatus in which a drying process of drying a substrate using a processing fluid in a supercritical state is performed. The substrate processing apparatus includes: a processing container in which the drying process is performed; a discharge valve provided in a discharge flow path that discharges the processing fluid from the processing container; and a controller configured to control the discharge valve. When the inside of the processing container is decompressed from a first pressure at which the processing fluid is in the supercritical state to an atmospheric pressure, through a second pressure than the first pressure and a third pressure lower than the second pressure, the controller controls a valve opening degree of the discharge valve so that the decompression rate is equal from the second pressure to the third pressure.