PURPOSE: To provide the titled composition having improved molding shrinkage, moisture-absorption, rigidity, toughness, etc., keeping the characteristics of the base resin, by compounding a specific resin to a polyamide, and dispersing the resin uniformly in the polyamide in the form of microscopic particles.

CONSTITUTION: (A) 45W70(wt)% polyamide composed of the recurring unit of formula I and/or formula II (x, y and z are 1W10) and having a weight- average molecular weight of preferably 40,000W90,000 (e.g. polycaprolactam, polyhexamethylene adipamide, etc.) is blended uniformly with (B) 55W30% copolymer composed of (B1) 3W20% 6-membered ring anhydride unit of formula III (R1 and R2 are H or methyl), (B2) 1W80% methyl methacrylate unit, (B3) 1W65% aromatic vinyl compound unit, and (B4) 0.5W10% methacrylic acid or acrylic acid unit, and having a weight average molecular weight of 100,000W500,000, by melting and kneading. The copolymer forms a disperse phase having an average particle diameter of ≤0.7μ in said composition.