Provided is a large-capacity ultrasonic space-sterilizing humidifier using an aqueous hypochlorous acid solution, wherein contaminants in humidified air are prevented from becoming included in humidifying water, the hypochlorous acid concentration in the humidified air is sufficiently maintained and a space-sterilizing effect is adequately exhibited. The ultrasonic space-sterilizing humidifier comprises a storage tank 2 storing an aqueous solution of hypochlorous acid, an ultrasonic generator 3 installed inside the storage tank 2, generating a hypochlorous acid-containing mist, an air duct 8 extending upwards from the ultrasonic generator 3, blowing means 4 for blowing the mist into the air duct 8, water-catching means 9 provided near the bottom end of the air duct 8, for collecting water droplets that have become adsorbed onto the inside wall of the air duct 8, and a discharge tube 11 mounted on the water-catching means 9, by which adsorbed water droplets are discharged to the outside.
