A hard-carbon-film-coated substrate includes in stacked sequence a substrate, an intermediate layer, and a hard carbon film. The substrate consists of a metal or an alloy mainly composed of Ni or Al, or stainless steel. The intermediate layer is mainly composed of Ru, Si, Ge or carbon, or is a mixed layer including Ru, Si, or Ge mixed with at least one of carbon, nitrogen or oxygen, with a composition gradient across its thickness. An apparatus for forming the coated substrate especially includes means for forming the intermediate layer and means for forming the hard carbon film in the same vacuum chamber.