To efficiently reduce amounts of unnecessary components such as unreacted phenols or a monofunctional component in the production of a phenol resin obtained by the reaction of phenol and dicyclopentadiene.

A method for producing a phenol resin is provided, including a reaction step of reacting dicyclopentadiene with phenol in the presence of a Lewis acid catalyst, a catalyst removal step, and a distillation step of distilling the reaction product at a temperature of 180°C or higher and 250°C or lower in the reaction vessel and a reduced pressure of 10 KPa or lower, while adding a solvent into the reaction vessel, so as to reduce the content of a monofunctional component having only one phenolic hydroxyl group in the molecule to less than 2%. Preferably the Lewis acid catalyst is a boron trifluoride complex, the solvent is a mixture solvent of water and an organic solvent, and the organic solvent has a boiling point of 110°C or higher.