PROBLEM TO BE SOLVED: To provide a phenolic resin and an epoxy resin, and production methods of these resins which have excellent fluidity and exhibit, in a cured product thereof, high flame retardancy, high adhesiveness to a substrate, and a low coefficient of linear expansion, and to provide a curable composition using the above resins, a cured product of the composition, a semiconductor encapsulation material, and a printed wiring board.SOLUTION: The phenolic resin has a resin structure obtained by reacting an alkylphenol, a &bgr;-naphthol compound, and formaldehyde in the absence of a catalyst. The phenolic resin comprises, as essential components, a phenolic hydroxyl group-containing compound (x1) and a phenolic hydroxyl group-containing compound (x2), in which a ratio [(x1)/(x2)] of contents of the above compounds calculated by liquid chromatography ranges from 3 to 100.
