A substrate processing apparatus includes a processing vessel; and a processing fluid supply configured to supply a processing fluid in a supercritical state into the processing vessel. The processing fluid supply includes a fluid supply line; a cooling device provided in the fluid supply line, and configured to cool the processing fluid in a gas state to produce the processing fluid in a liquid state; a pump positioned downstream of the cooling device; a heating device positioned downstream of the pump, and configured to heat the processing fluid in the liquid state to generate the processing fluid in the supercritical state; a first flow rate adjuster positioned between the pump and the heating device, and configured to adjust a supply flow rate of the processing fluid supplied to the processing vessel; and a controller configured to control the first flow rate adjuster.