Provided is a technique for enabling a liquid of microbial cells having an enzymatic activity to be easily stored and used. The technique is a method for killing a microorganism while maintaining the enzyme titer of a microbial cell liquid, characterized by including adjusting the pH of a liquid of microbial cells having an enzymatic activity, and then performing a heating treatment of the liquid, and also the technique is a method for killing a microorganism while maintaining the enzyme titer of a microbial cell liquid, characterized by including adding a carbohydrate to a liquid of microbial cells having an enzymatic activity, and then performing a heating treatment of the liquid.