The present invention provides a manufacturing method of a semiconductor device that has a rapid film formation rate and high productivity, and to provide a substrate processing apparatus.The method comprises the steps of loading a substrate into a processing chamber; forming a thin film having a desired thickness on the substrate by setting as one cycle the step of supplying into the processing chamber adsorption auxiliary gas for aiding an adsorption of a source gas vaporized from a liquid source on the substrate and causing this adsorption auxiliary gas to be adsorbed on the substrate, the step of supplying the source gas into the processing chamber, causing the source gas to react with the adsorption auxiliary gas on the substrate, and causing this source gas to be adsorbed on the substrate, and the step of supplying a reaction gas into the processing chamber and causing this reaction gas to react with the source gas adsorbed on the substrate, and repeating this cycle a plurality of times; and unloading the substrate provided with the thin film from the inside of the processing chamber.