PURPOSE: To provide the title compsn. which can be obtained continuously and simply at an excellent working efficiency and has excellent heat resistance, adhesion properties, electrical characteristics and flexibility, containing a prepolymer of a polyaminobismaleimide, novolak type and bisphenol F type epoxy resins and an imidazole curing agent.

CONSTITUTION: 100pts.wt. prepolymer (A) of a polyaminobismaleimide is kneaded with 10W200pts.wt. novolak type epoxy resin (B), 20W200pts.wt. bisphenol F type epoxy resin (C), a 0.3W60pts.wt. imidazole curing agent (D) such as 4,4'- methylene bis(2-ethyl-5-methylimidazole), etc. and optionally, a filler (E) such as silica powder, NBR, an alcohol-soluble nylon, polyvinyl butyral, etc. (F).