PURPOSE: To produce a large-area thin film of a superconductor having a uniform film compsn. and film thickness by disposing a gaseous org. metal compd. guiding pipe in the form of a multiple concentrical type around an oxygen-contg. gas guiding pipe and mixing both gases just before a substrate.

CONSTITUTION: The oxygen-contg. gas guiding pipe 7 is inserted into the center of a reaction tube 2 and the gaseous org. metal compd. guiding pipe 3 is disposed in the form of the multiple concentrical type. A gas introducing pipe 1 is connected to the gaseous org. metal compd. guiding pipe 3 and the gaseous org. metal compd. [La(C5H5)3, Sr(C5H5)2, Cu(acac)2] is introduced into the reaction tube 2. The reaction tube 2 is heated by a heater 8 to prevent the condensation of the gas to the tube wall. Inert gases are introduced from a gas introducing pipe 4 and the oxygen-contg. gas is discharged in front (about 10W20cm) of the substrate 5 heated by a heater 9 through the guiding pipe 7. The gaseous org. metal compd. and the oxygen-contg. gas are thereby quickly and uniformly mixed and the thin superconductive film having the uniform film compsn. and film thickness is formed on the substrate 5.