PURPOSE: To obtain the title composition which is thermosetting, solvent-free, thus having high storage stability and excellent operability, because it is liquid, by mixing a specific resin composition with a polyamine and thermosetting the mixture.

CONSTITUTION: The subject composition is obtained by mixing (A) a resin composition which is produced by mixing, under heat, (i) a polymaleimide resin of formula I (R1 is n-valent organic group; Xa, Xb are H, halogen, organic group; n is 1W4) such as hexamethylene bismaleimide, (ii) an epoxy resin bearing at least 2 epoxy groups in the molecule such as bisphenol-A type epoxy resin and (iii) a compound bearing 1 alcoholic or phenolic hydroxyl group and one or more epoxy groups such as a compound of formula II and (B) a polyamine such as m-phenylenediamine, preferably at a weight ratio of 100:(10W50) and thermosetting.