A substrate processing apparatus enables an efficient collection of a solvent vapor discharged via a nozzle onto a wafer on which a resist pattern is formed. A retaining base that retains the wafer is moved relative to the nozzle, which includes a nozzle head. A pair of leakage preventing portions are disposed opposite to each other across the nozzle head. Each of the leakage preventing portions has an opening via which the solvent vapor discharged out of the discharge opening can be sucked, or a solvent vapor blocking gas can be discharged selectively. A solvent vapor supply source and a gas supply source are switchably connected to the supply opening of the nozzle head via a first switching valve. An exhaust pump and a solvent-vapor-blocking gas supply source are switchably connected to the openings of the leakage preventing portions via a second switching valve.