When forming a TiN film to be formed as a metallic hard mask for etching a film formed on a substrate to be processed, a first step and a second step are repeated a plurality of times to form a TiN film having reduced film stress. In the first step (step 1), the substrate to be processed is conveyed into a processing chamber, TiCl4 gas and a nitriding gas are fed into the processing chamber, the interior of which being kept in a depressurized state during this time, and a plasma from the gases is generated to form a TiN unit film. In the second step (step 2), a nitriding gas is fed into the processing container, a plasma of the gas is generated, and the TiN unit film is subjected to plasma nitriding.