Abstract: Herein described is a process for forming ohmic electrodes to a diamond film, comprising the steps of implanting the ions of at least one element selected from the group consisting of B, Li, Na, Ar, C, Ti, W, Ta, Mo, Fe, Ni and Co on the diamond film at the surface areas to be formed with electrodes by an ion implantation method so as to form interface levels in the vicinity of the surface areas to be formed with electrodes, forming electrodes to the ion implanted areas, and heating the diamond film formed with the electrodes at a temperature of 400.degree. C. or more. With this process charge carriers can be moved between electrodes and the diamond film through the interface levels to thereby obtain ohmic electrode diamond film contacts, and also the surface recombination speed of the charge carriers is increased for reducing the contact resistances between the electrodes and the diamond film to thereby obtain ohmic electrode-diamond film contacts each having the small contact resistance.