A substrate processing apparatus includes a fluid supply unit that supplies a fluid that includes a pressurized vapor or mist of a purified water, a processing liquid supply unit that supplies a processing liquid that includes at least sulfuric acid, and a nozzle that includes a first discharge port that discharges a fluid that is supplied from the fluid supply unit, a second discharge port that discharges a processing liquid that is supplied from the processing liquid supply unit, and a guiding route that is communicated with the first discharge port and the second discharge port and guides a mixed fluid of a fluid that is discharged from the first discharge port and a processing liquid that is discharged from the second discharge port, where a cross-sectional area of the guiding route is greater than a cross-sectional area of the first discharge port.