The present invention provides a polyfunctional phenolic resin and a polyfunctional epoxy resin having low viscosity and having excellent mechanical properties and heat resistance of a cured product to be obtained, a curable resin composition containing these, and a cured product thereof. Specifically, provided are a polyfunctional phenolic resin formed with a naphthol structure optionally having a substituent on an aromatic ring and a catechol structure optionally having a methyl group as a substituent on an aromatic ring bonded together via a methylene group optionally having a substituent, a polyfunctional epoxy resin obtained by epoxidizing the polyfunctional phenolic resin, a curable resin composition containing any of these, and a cured product thereof.