Provided is a liquid preparation for disinfecting a contact lens, which can advantageously be produced by a process employing filtration sterilization and is excellent in stability, and further, provided is a method of industrially advantageously producing the liquid preparation for disinfecting a contact lens, which has such excellent characteristics. A cationic polypeptide antimicrobial agent and Hypromellose 2910 as a thickening agent are used together, dissolved in an aqueous medium, and the kinematic viscosity at 25°C is adjusted to 0.8 mm2/s to 15 mm2/s to obtain a liquid preparation for disinfecting a contact lens.
