A novel thermosetting compound which is speedily curable, generates no by-products during curing and gives cured products having excellent heat resistance and inflammability.A thermosetting compound characterized in containing, per molecule, at least one structural unit represented by the formula (A) and at least one structural unit represented by the formula (B) in a (A)/(B) molar ratio of 1/0.25 to 1/9, said structural units being bonded directly or via at least one organic group with one another; ##STR1## wherein R.sup.1 is a methyl group, a cyclohexyl group, a nonsubstituted phenyl group or a phenyl group substituted with at least one substituent, and each hydrogen atom on the aromatic rings of (A) and (B), except for one of hydrogen atoms on ortho-positions of the hydroxy group in the aromatic ring of (A), may optionally be replaced with a substituent.