There is provided a means for sterilizing lactoferrin at a high temperature in a short time while maintaining the activity of the lactoferrin. The present technology provides a method for producing a lactoferrin-containing aqueous solution, including a sterilization step of heat-sterilizing a lactoferrin-containing aqueous solution, in which the total mass content of proteins other than lactoferrin is 1/12 or less of the mass content of lactoferrin, at a temperature of 100°C or more. The present technology also provides a lactoferrin-containing aqueous solution in which the total mass content of proteins other than lactoferrin is 1/12 or less of the mass content of lactoferrin, and which does not contain living bacteria.