PURPOSE: To provide a silicon nitride whisker-reinforced composite material having improved strength by compounding the silicon nitride whiskers obtd. from amorphous silicon nitride powder and aluminum at a specific ratio.

CONSTITUTION: The composite material is produced from 5W50vol% silicon nitride whiskers obtd. from amorphous silicon nitride and 95W50vol% aluminum or the alloy thereof. The whiskers are produced by compounding iron, silicon dioxide, etc. as an additive to the amorphous silicon nitride powder and heating up the powder for a prescribed period from about 1,000°C up to about 1,800°C in a non-oxidative atmosphere. The compounding ratio of the above-mentioned additive is about 0.05W10pts.wt. by 100pts.wt. amorphous silicon nitride powder and the resulted whiskers are the needle-like single crystal having about 10W100μ length and about 0.1W1μ diameter. The specific surface area thereof is about 2W10m2/g and the oxygen content is about 1W4wt%. The composite material having about 70W80kg/m2 deflection strength is thus obtd.