In a method of forming a tungsten film, an initial tungsten film and a main tungsten film are formed on an underlying film of a substrate. The initial tungsten film is formed on the underlying film by sequentially supplying a tungsten chloride gas and a reduction gas into a chamber while supplying a purging gas between the supplies of the tungsten chloride gas and the reduction gas, or by simultaneously supplying the tungsten chloride gas and the reduction gas. The main tungsten film is formed on the initial tungsten film by sequentially supplying the tungsten chloride gas and the reduction gas into the chamber while purging an inside of the chamber between the supplies of the tungsten chloride gas and the reduction gas. A supply amount of the tungsten chloride gas in forming the initial film is smaller than that in forming the main tungsten film.