Disclosed is a phenolic resin having flame retardance, fast curing property and low melt viscosity, which is useful for a curing agent for epoxy resin-based semiconductor sealing materials. Also disclosed are a method for producing such a phenolic resin and use of such a phenolic resin. Specifically disclosed is a phenolic resin obtained by reacting a phenol, a bismethylbiphenyl compound and an aromatic aldehyde at such a ratio that the molar ratio of the total of the bismethylbiphenyl compound and the aromatic aldehyde relative to the phenol is 0.10-0.60, and the aromatic aldehyde/the bismethylbiphenyl compound (molar ratio) is from 5/95 to 50/50. Also specifically disclosed is an epoxy resin composition composed of such a phenolic resin and an epoxy resin.