Disclosed is a process for purifying an enzyme contained in a solution such as cell extract liquor or fermentation culture liquor. The crude enzyme solution is brought into contact with either a strongly acidic cation exchange resin of high porous type or a strongly basic anion exchange resin of high porous type to adsorb the enzyme on the resin. An eluting agent is then passed through the resin to elute out the enzyme as a purified enzyme solution.