A substrate processing apparatus can suppress particle generation on a substrate, and can reduce a consumption amount of a processing liquid. A substrate processing apparatus 1 includes a processing chamber 30 having a processing space 31 in which a substrate W is processed; a vaporizing tank 60, configured to store the processing liquid therein, having a vaporization space 61 in which the stored processing liquid is allowed to be vaporized; a decompression driving unit 70 configured to decompress the vaporization space 61; and a control unit 18. The control unit 18 vaporizes the processing liquid into the processing gas by decompressing the vaporization space 61 without through the processing space 31, and then, vaporizes the processing liquid into the processing gas by decompressing the vaporization space 61 through the processing space 31, and supplies an inert gas into the vaporization space 61.