Provided are: a method for producing a purified lactase-containing composition, which comprises removing protease contaminating the lactase selectively by a simple means a lactase-containing composition and a milk product containing the lactase-containing composition.A method for producing a lactase-containing composition having a reduced protease content, said method being characterized by dissolving a composition containing both lactase and protease in a salt-containing aqueous solution having an electrical conductivity of 2 to 45 mS/cm, bringing the resultant solution into contact with an ion exchange resin, and then collecting a fraction that is not adsorbed onto the ion exchange resin.
