PURPOSE: To efficiently form a thin film having a uniform film thickness by disposing a light introducing pipe to the center of a reaction tube, disposing an oxygen-contg. gas guiding pipe and gaseous org. metal compd. guiding pipe successively in a concentrical type to the outside thereof and discharging an oxygen-contg. gas just before a substrate.

CONSTITUTION: The light introducing pipe 8 is disposed to the center of the reaction tube 3 to introduce light through a lens 9 onto the substrate 2. The oxygen-contg. gas guiding pipe 7 and the gaseous org. metal compd. guiding pipes 6 are successively provided in the concentrical type so as to enclose the light introducing pipe 8. Introducing pipes 5 are connected to the org. metal compd. guiding pipes 6. The introducing pipes 5 and the reaction tube 3 are heated by heaters. The gaseous org. metal compd. [La(C5H5)3, Sr(C5H5)2, Cu(acac)2] is introduced through the introducing pipes 5 and inert gases (He, Ar, etc.) are introduced as a carrier gas through an introducing pipe 4. The oxygen- contg. gas is discharged just before (about 10W20cm) the heated substrate 2 from the oxygen-contg. gas guiding pipe 7. The thin film is thereby efficiently formed while the explosion and the early reaction except on the substrate 2 are prevented.