PURPOSE: To provide a device of special constitution which converts a nonsuperconducting material to a superconductor by applying a protective film for preventing the thin film of a metal which is mounted on a blank and has negative sensitivity against its oxidation or other contamination on this thin film.

CONSTITUTION: The superconducting device 10 includes the blank 12 on which the superconducting thin film 15 is deposited by evaporation. The blank 12 consists of either a conductive or a nonconductive material and a mica sheet coated with NaCl is adaptable to practicable use. The thin film 15 preferably consists of Cr or Cr alloy deposited by evaporation on the blank 12 to such a thickness at which the film has the high negative sensitivity and acts as the superconductor at room temp. Next, the protective coating film 17 is applied on the film 15 in order to protect the film against a harmful environment and oxidation. The film 17 comprises a transition metal or noble metal and Pd and silver have an excellent protective property and orients the sensitivity to the negative direction and therefore, the superconducting property of the film 15 is improved as well.