A substrate processing apparatus includes a discharge part including a nozzle configured to discharge a processing liquid onto a substrate; a liquid feeder configured to feed the processing liquid to the discharge part; a replenishment part configured to replenish the liquid feeder with the processing liquid to be fed to the discharge part; a connector including a switching valve configured to open/close a flow path between the replenishment part and the liquid feeder; a filter configured to remove foreign matters contained in the processing liquid; a replenishment preparation part configured to open the switching valve after reducing a pressure difference between the inside of the replenishment part and the liquid feeder; and a replenishment controller configured to start replenishment of the processing liquid from the replenishment part to the liquid feeder in a state in which the switching valve is opened by the replenishment preparation part.