A substrate processing apparatus comprises: a process chamber configured to accommodate a substrate; a gas supply line configured to supply gas into the process chamber; and an exhaust line configured to exhaust the inside of the process chamber. In the substrate processing apparatus, the gas supply line comprises: a preheating unit configured to preheat the gas before supplying the gas into the process chamber; a metal pipeline configured to supply the preheated gas into the process chamber; and a heat dissipation member covering the outer periphery of a bend section formed in the metal pipeline.