A tungsten film forming method for forming a tungsten film on a surface of a substrate while heating the substrate in a depressurized atmosphere in a processing chamber includes forming an initial tungsten film for tungsten nucleation on the surface of the substrate by alternately repeating a supply of WF6 gas which is raw material of tungsten and a supply of H2 gas which is a reducing gas in the processing chamber while performing a purge in the processing chamber between the supplies of the WF6 gas and the H2 gas and adsorbing a gas containing a material for nucleation onto a surface of the initial tungsten film. The film forming method further includes depositing a crystallinity blocking tungsten film for blocking crystallinity of the initial tungsten film by supplying the WF6 gas and the H2 gas into the processing chamber.