A film forming apparatus includes a processing chamber, and a mounting table disposed in the processing chamber to mount a substrate thereon. The film forming apparatus further includes a gas shower head having gas supply holes and including a central region facing a central portion of the substrate and a peripheral region facing a peripheral portion of the substrate, a first processing gas supply unit for supplying a first processing gas to the central region, a second processing gas supply unit for supplying a second processing gas to the central region, an energy supply unit for supplying energy to react the first processing gas with the second processing gas on the substrate, and a purge gas supply unit for supplying a purge gas to the central region and the peripheral region when one of the first and the second processing gas is switched by the other.