A cure-accelerator for an epoxy resin, which comprises a compound of the formula (I), R.sub.1 R.sub.2 NCONH--Ar--NHCONR.sub.3 R.sub.4 (I) wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are C.sub.1 -C.sub.3 lower alkyl groups which may be the same or different, and Ar is a substituted tolylene group of the formula (II) ##STR1## wherein R.sub.5 and R.sub.6 are C.sub.1 -C.sub.4 lower alkyl groups which may be the same or different) or a 1,5-naphthylene group.