PURPOSE: To obtain a composite material having excellent strength, modulus, toughness and resistance to heat and wear, by compounding a surface treating agent-treated aggregate with a thermosetting compsn. matrix and molding the resulting composite material by thermosetting.

CONSTITUTION: The surface of an aggregate having hydrogen, halogen, hydroxyl, carboxyl, etc., on its surface is coated with a surface treating agent mainly composed of an arom. crosslinking agent composed of a mono- or polycyclic arom. ring having at least two hydroxylmethyl or halomethyl groups and the coated aggregate is heat-treated. A matrix composed of a combination of a condensed polycyclic arom. compd. mainly composed of a bicyclic compd. with the above-mentioned arom. crosslinking agent and an acid catalyst is compounded with the aggregate which has been coated above. The resulting composite material is heated at 100W400°C to plasticize it and then molded by thermosetting. The cured molding is heated at 100W400°C and kept at that temp. for 30min to 100hr to post cure it, thus obtaining the desired composite material.