PURPOSE: To obtain a new naphthol compound useful as a diluent, a denaturant or a modifier for an epoxy resin curing agent and imparting excellent workability to the agent and capable of providing a cured product having a high glass transition temperature, heat resistance, moisture resistance, adhesiveness and flexibility and free from occurrence of crack.

CONSTITUTION: This compound is a naphthol compound having ≥2 allyl groups and expressed by formula I (R1 and R2 are each H or allyl; R3 is H or OH and when R3 is H, the position of OH is 1-position, that is α-position), e.g. diallyl α-naphthol of formula II. The compound of formula I is obtained by adding, e.g. a base and water to a naphthol and as necessary, an organic solvent, uniformly mixing these components to phenoxidize the naphthol and carrying out allylation reaction while dropping an allyl halide to the solution system for a long time and subjecting the reactional product to Claisen's rearrangement by high-temperature heating. This curing agent for epoxy resins is obtained by adding an aldehyde condensate of a naphthol to the naphthol compound of formula I. This epoxy resin composition is obtain by further adding the curing agent to an epoxy resin.