A phenol resin composition used as a curing agent for an epoxy resin includes a naphthol novolac resin (a1) represented by general formula (1) (wherein R1 and R2 each independently represent a hydrogen atom, an alkyl group, or an alkoxy group, and n is a repeating unit and an integer of 1 or more), and a compound (a2) represented by general formula (2) (wherein R1 and R2 each independently represent a hydrogen atom, an alkyl group, or an alkoxy group), wherein the total ratio of compounds with n=1 and n=2 in the general formula (1) present in the composition is in the range of 10 to 35%, the average of n in the general formula (1) is in the range of 3.0 to 7.0, and the content of the compound (a2) in the composition is 1 to 6%.