Abstract: A process for coating a substrate surface with a diamond-like carbon film, in which a starting material gas comprising a hydrocarbon compound is introduced into a Hall accelerator ion source with an inner pressure thereof reduced to 1.times.10.sup.-5 to 1.times.10.sup.-1 Torr, an ion beam in which 80% or more of the ion beams formed have an impinging energy in the range of 100 to 1500 eV is formed in the ion source, and irradiated onto a substrate comprising various kinds of materials in a vacuum chamber, to thereby coat the substrate surface with a diamond-like carbon film with a strong adhesion to an extent such that is can with stand practical application.