A method of forming a pseudo-diamond film on a base body, the method comprising a first step of irradiating carbon ions onto a surface of a base body from an assisting ion gun to form a mixture layer comprising base body material atoms and carbon atoms; a second step of simultaneously vapor-depositing the carbon atoms from a vapor deposition source and irradiating hydrogen ions from the assisting ion gun onto the mixture layer to form pseudo-diamond cores on the mixtures layer; and a third step of vapor-depositing carbon atoms from the vapor deposition source and irradiating hydrogen ions from the assisting ion gun onto the pseudo-diamond cores to form a pseudo-diamond film on the pseudo-diamond cores.