In a DLC film-formed material, an intermediate layer is disposed between a substrate and a DLC film. The intermediate layer is a composite layer containing a component metal atom derived from the substrate and a diamond-like carbon. For example, such intermediate layer can be formed by applying a negative bias to the substrate while reducing the absolute value of the negative bias with time, in a plasma layer formation process. A carbon target or a hydrocarbon gas can be used as a carbon source.