PURPOSE: To easily produce easily pulverizable silicon nitride having high αand high specific surface area by using a rather inexpensive metal silicon source material without requiring a troublesome post treatment such as a special pulverizing process and wet refining treatment.

CONSTITUTION: A source material for nitridation comprising 100 pts.wt. metal silicon powder and 30-100 pts.wt. silicon nitride powder having ≥85% α rate and 5-20m2/g specified surface area is heated and nitrided in an atmosphere containing nitrogen and/or ammonia with ≤0.2wt.% total amt. of oxygen and water to the metal silicon powder. The source material is heated for nitridation while the difference between the inner temp. of the source material for nitridation and the ambient temp. is controlled to ≤50°C. Thus, ≥30% of the metal silicon powder is nitrided up too 1200°C and ≥90% of the powder is nitrided up to 1350°C.