Manufacturing cost or energy consumption of a substrate processing apparatus can be reduced. The substrate processing apparatus includes a substrate loading/unloading unit (a substrate transit chamber 12) that transfers a substrate 2 accommodated in a carrier 3; a substrate transfer chamber 14 (25) communicating with the substrate loading/unloading unit via a substrate loading/unloading port 37 (39); a plurality of substrate processing chambers 15 to 24 (26 to 35) arranged along the substrate transfer chamber 14 (25); a substrate transfer device 36 (38) provided in the substrate transfer chamber 14 (25) and configured to transfer the substrate 2 between the substrate loading/unloading unit and the substrate processing chambers 15 to 24 (26 to 35); and a clean air flowing unit 41 (42) that allows clean air to flow along the substrate transfer chamber 14 (25).