Disclosed are an apparatus and a method for reducing a processing liquid consumed for removing bubbles from a new filter unit, and shortening a start-up time when the filter unit is attached in a processing liquid supply passage. The method includes: filling the processing liquid into a new filter unit, decompressing inside of the filter unit into a first pressure atmosphere in order to remove bubbles from the filter unit, boosting a pressure of the inside of the filter unit, flowing the processing liquid into the filter unit from a primary side of the filter unit, and supplying the processing liquid flowing from the filter unit to an object to be processed through a nozzle thereby performing a liquid processing and quickly removing the bubbles.