Curing agents for epoxy resins which contain as the active ingredient at least one member selected from among compounds represented by general formula (I) and salts thereof: wherein X is -(CH2)n- or -(CH2)l-Y-(CH2)m-; Y is -N(R )-, -O- or -S-; R is C1-C8 alkyl or amino; n is a number of 2, 3, or 5 to 11; and l and m are each a number of 1 to 8.