A method of forming a Ti film on a substrate disposed in a chamber by introducing a processing gas containing a TiCl4 gas as a Ti source and a H2 gas as a reducing gas and by generating plasma in the chamber, includes introducing an Ar gas as a plasma generation gas into the chamber, converting the Ar gas into plasma to generate Ar ions, and acting the Ar ions on the Ti film to promote desorption of Cl from the Ti film.