A method of forming a low-K dielectric film, comprises the steps of placing a substrate carrying thereon a low-K dielectric film on a stage, heating the low-K dielectric film on the stage, processing the low-K dielectric film by plasma of a processing gas containing a hydrogen gas, the plasma being excited while supplying the processing gas over the low-K dielectric film, wherein the plasma is excited within 90 seconds after placing the substrate upon the stage.