Disclosed is a processing liquid supplying apparatus. The apparatus includes: a processing liquid supply source configured to supply a processing liquid for processing a substrate to be processed; an ejection unit configured to eject the processing liquid to the substrate to be processed; a filter device configured to remove foreign matters in the processing liquid; a supply pump and an ejection pump which are provided in the supply path at a primary side and a secondary side of the filter device, respectively; and a control unit configured to output a control signal to decompress and degas the processing liquid supplied from the processing liquid supply source by using one of the supply pump and the ejection pump, and subsequently, pass the degassed processing liquid through the filter device beginning from the primary side to the secondary side of the filter device by using the supply pump and the ejection pump.