The present invention provides a method of producing tert-leucine, which includes reacting tert-leucine with substituted benzenesulfonic acid represented by the following formula (1)
wherein R1 and R2 are each independently a hydrogen atom, an alkyl group or a halogen atom, except a compound wherein R1 and R2 are both hydrogen atoms, in a solvent, to give tert-leucine.substituted benzenesulfonate represented by the following formula (2)
wherein R1 and R2 are the same substituents as above, separating the salt by crystallization and then dissociating the salt. According to the present invention, a production method of tert-leucine is provided, which includes forming a tert-leucine salt hardly soluble in a solvent and crystallization thereof to efficiently recover tert-leucine from the solvent.