A preparation method of a modified naphthol resin includes the following. A nitration reaction and a hydrogenation reaction are sequentially performed on a naphthol resin to form a modified naphthol resin with an amino group in a structure. A solvent used in the hydrogenation reaction includes tetrahydrofuran, toluene, isopropanol, an amide solvent, or an above-mentioned co-solvent.

Provided are an anion exchange resin being capable of producing an electrolyte membrane, a binder for forming an electrode catalyst layer, and a battery electrode catalyst layer, which has excellent electrical properties (anion conductivity) and chemical properties (gas permeability and water uptake property), an electrolyte membrane and a binder for forming an electrode catalyst layer formed from the anion exchange resin, and a battery electrode catalyst layer formed from the binder for forming an electrode catalyst layer.

For example, used is an anion exchange resin in which a hydrophobic unit being composed of divalent hydrophobic groups including a bisphenol residue having an alicyclic structure, which are repeated via carbon-carbon bond, a hydrophobic unit being composed of hydrophobic groups of a plurality of aromatic rings bonded to each other via a divalent fluorine-containing hydrocarbon group, which are repeated via carbon-carbon bond, and a hydrophilic unit having a fluorene ring bonded to an anion exchange group-containing group are bonded via carbon-carbon bond.