To provide a curing agent suitable for an epoxy resin composition imparting a cured product excellent in low hygroscopicity and low stress, particularly useful for sealing semiconductors.

The curing agent for epoxy resins comprises a phenol compound represented by general formula (1) [wherein R1s are mutually same or different and each represents a hydrogen atom, a 1-10C alkyl group, aryl group, aralkyl group, a 1-10C alkoxy group or a halogen atom; R2s are mutually same or different and each represents a hydrogen atom, a 1-10C alkyl group, aryl group, aralkyl group or a 1-10C alkoxy group; Z is a divalent group containing a carbon ring such as a substituted or an unsubstituted phenylene group or naphthylene group] in an amount of 5-100 wt.% based on total curing agent amount for epoxy resins.