A substrate processing apparatus includes: a processing room in which a semiconductor substrate may be treated by a process; a cooling unit positioned to cool the processing room, the cooling unit configured to convey cooling fluid; and a temperature-adjusting unit that alters the temperature of the cooling fluid supplied into the cooling unit. The temperature-adjusting unit has a cycling circuit. The cycling circuit has a compressor configured to compress a refrigerant, a condenser configured to condense the compressed refrigerant, an expander configured to expand the condensed refrigerant, the expander including a plurality of expansion valves arranged in parallel, and an evaporator configured to evaporate the expanded refrigerant, the evaporator positioned to cool the cooling fluid.