A substrate processing apparatus includes a chamber, a supply pipe, a discharge pipe, a trap section, a heater, a buffer section, and a cooling pipe. The chamber houses a substrate. The supply pipe supplies a processing gas into the chamber. The discharge pipe discharges a gas produced in the chamber. The trap section is disposed in the discharge pipe. The heater heats the trap section. The buffer section is disposed downstream of the trap section in the discharge pipe. The cooling pipe cools the buffer section.