[Problem] To provide a means for stabilizing a lactase solution [Solution] Disclosed are lactase solutions having excellent thermal stability and methods for the stabilization of lactase solutions. A lactase solution comprising sugar in an amount of 0.1 to 100 g/kg on the basis of the total mass of the lactase solution, wherein an amount of reducing sugar contained in the lactase solution is 2.0 mg/g or less. The solutions are useful in low lactose milk, derivatives and dairy products.