In a tungsten film forming method, a substrate having a recess is provided in a processing chamber, and a first tungsten film is formed on the substrate to fill the recess with a tungsten by simultaneously or alternately supplying WCl6 gas as a tungsten source and a reducing gas under a depressurized atmosphere of the processing chamber, and by reacting the WCl6 gas with the reducing gas while heating the substrate. Then, an opening is formed in the tungsten filled in the recess by supplying WCl6 gas into the processing chamber and etching an upper portion of the tungsten. Thereafter, a second tungsten film is formed on the substrate having the opening by simultaneously or alternately supplying the WCl6 gas and the reducing gas into the processing chamber, and by reacting the WCl6 gas with the reducing gas while heating the substrate.