Epoxy resin compositions which contain (1) an epoxy resin which has two or more epoxy groups in its molecule, (2) a polythiol compound which has two or more thiol groups in its molecule and (3) an accelerator which is (i) a solid dispersion-type amine adduct latent curing accelerator or (ii) the product of a reaction between a compound which contains one or more isocyanate groups in its molecule and a compound which has at least one primary and/or secondary amino group in its molecule, exhibit excellent curability at relatively low heating temperatures as well as a long working life.