To grow a good-quality nitrided compd. crystal having decreased defects on a substrate at low temp. by providing the subject apparatus with a nozzle made of zirconia packed with alumina fibers as a nozzle for introducing gaseous ammonia,

The nozzle 2 for introducing the gaseous ammonia into a reaction vessel 1 is constituted by connecting a nozzle body 21 made of zirconia to a stainless steel pipe 22 for introducing the gaseous ammonia from a raw material reservoir. The nozzle body 21 is formed by adhering an upstream part 21a formed by machining a zirconia block and boring the inside thereof and a downstream part 21b formed by providing the zirconia block with many fine holes 24 in a gas flow direction by an adhesive. Alumina fibers 23 are packed into the upstream part 21a. The gaseous ammonia introduced into the nozzle 2 is cracked with the heated alumina fibers 23 as a catalyst and is injected through the fine holes 24 onto the substrate 5. The cracked gaseous ammonia is heated by the wall surfaces of the fine holes 24 at the time of passing the same and is made readily reactable.