Provided is a substrate processing apparatus capable of suppressing accumulation of reaction products or decomposed matters on an inner wall of a nozzle and suppressing scattering of foreign substances in a process chamber. The substrate processing apparatus includes a process chamber, a heating unit, a source gas supply unit, a source gas nozzle, an exhaust unit, and a control unit configured to control at least the heating unit, the source gas supply unit and the exhaust unit. The source gas nozzle is disposed at a region in the process chamber, in which a first process gas is not decomposed even under a temperature in the process chamber higher than a pyrolysis temperature of the first process gas, and the control unit supplies the first process gas into the process chamber two or more times at different flow velocities to prevent the first process gas from being mixed.