Chemical reactions of superconducting raw materials with active oxygen atoms and their charged particles are accelerated by using at least oxygen plasma in the fabrication process of a superconductive body. Thereby an ionic crystal is grown in a short time, which provides stable superconducting materials of high quality such as high critical temperature and low resistivity. In another aspect, a substrate is irradiated simultaneously with streams of vapor of metal elements, of which a superconductive body is to be composed, and a stream of gas of ions generated in a plasma chamber and film growth is effected while keeping the substrate at a temperature higher than 400.degree. C. to produce a ceramic type superconductive thin film.