To provide a method for producing a tertiary butoxybenzene derivative by reacting a phenol compound with isobutylene in the presence of an acid catalyst, by which the unreacted isobutylene can quantitatively and efficiently be removed, recovered from the reaction solution and recycled.

This method for producing the tertiary butoxybenzene derivative by reacting a phenol compound with isobutylene in the presence of an acid catalyst, comprises (1) quantitatively dropping the reaction solution on a hot alkali aqueous solution to remove the unreacted raw materials and then distilling the residue to obtain the tertiary butoxybenzene derivative, or (2) quantitatively dropping the alkali-treated reaction solution on a heating medium to remove the unreacted raw materials and then distillingthe residue to obtain the tertiary butoxybenzene derivative.