<p>Disclosed is an apparatus for forming a compound thin film on the surface of a substrate, which is held in a sputtering film formation chamber, by reactive sputtering. The sputtering film formation chamber is provided with a first film property-adjusting gas introducing means for introducing a film property-adjusting gas, which is used for adjusting the film properties of a compound thin film to be formed on the front surface of the substrate, onto the back surface of the substrate.</p>
