A substrate processing apparatus in accordance with the present invention includes a process chamber configured to accommodate a substrate, a gas supply line configured to supply a gas to an inside of the process chamber, and an exhaust line configured to exhaust the inside of the process chamber. The gas supply line of the substrate processing apparatus includes a preheating unit preheating the gas supplied from a gas source, a metal pipeline having an angled section wherein the metal pipe line connects the preheating unit and the inside of the process chamber to supply the gas preheated by the preheating unit into the process chamber, and a heat dissipation member covering the angled section to dissipate heat from the angled section.