PURPOSE: To obtain the titled composition improved in flexibility and impact resistance without impairing heat resistance and enhanced in dimensional stability without impairing water absorptivity, by incorporating a bismaleimide-based imide resin with a bifunctional silicone monomer.

CONSTITUTION: The objective composition can be obtained by incorporating (A) 100pts.wt. of a bismaleimide-based imide resin synthesized chiefly from a compound of formula (R is divalent organic group containing group such as alkyl or arylene, or group containing two phenylene groups linked through CH2, O, etc.) with (B) 5W25pts.wt. of a bifunctional silicone monomer having such group as to reactive with maleimide group and be capable of addition polymerization (e.g., OH, NH2) (e.g., dimethylsilanediol, dianilinodimethylsilane) and, depending on the uses to be aimed such as for improving mechanical strength or dimensional accuracy, (C) ≤150pts.wt. of ingredient(s) such as glass fiber or talc followed by kneading using e.g., a kneader.