Disclosed is a substrate processing system, including: a processing chamber to process a substrate; a vaporizing unit to vaporize a material of liquid; a supply system to supply the processing chamber with gas of the material vaporized by the vaporizing unit; an exhaust system to exhaust an atmosphere in the processing chamber; and a cleaning liquid supply system to supply the vaporizing unit with cleaning liquid for cleaning a product deposited in the vaporizing unit, wherein the cleaning liquid supply system supplies at least two kinds of cleaning liquids into the vaporizing unit so that the product can be removed from the vaporizing unit by action of the two kinds of cleaning liquids on the product.