PURPOSE: To obtain α-silicon nitride powder having excellent high-temperature strength and toughness, comprising silicon nitride having specific, β formation ratio as peritectic.

CONSTITUTION: This α-silicon nitride comprises silicon nitride having ≥90% βformation ratio as peritectic. The α-silicon nitride is obtained by the following method. Namely, a nitrogen-containing compound and/or a amorphous silicon nitride as a raw material is blended with 2W10wt.% based on theoretical amount of silicon nitride formed from the raw material of silicon nitride powder which has ≥90% β formation ratio, 10W20m2/g specific surface area and ≤1,000ppm sum of Fe, Al, Ca and Mg (calculated as ratio of the silicon nitride powder based on the raw material). Then the mixture is heated and crystallized in a nonoxidizing atmosphere containing nitrogen or ammonia at ≥1,450°C.