PURPOSE: To enable an increased water level to be decreased down to a predetermined value within a short period of time without using any returning pipe by a method wherein a humidifier for atomizing liquid stored in a first liquid tank is arranged in the first liquid tank having a predetermined height and formed with its upper end being opened into a second liquid tank.

CONSTITUTION: A space 9 inside an inner wall 8 forms an outer water tank of a humidifying and cold air feeding machine 1, and an inner water tank 11 is arranged at a higher location than a bottom part of the outer water tank 9. Then, a humidifier 12 utilizing an ultrasonic vibrating element is fixed to a center part of the bottom part of the inner water tank 11. A water tank height of the inner water tank 11 has such a size as one in which it has a size (65mm) added with a predetermined value (40mm) to a size (25mm) ranging from a vibrating surface 12a of the ultrasonic vibrating element to the bottoms part of the inner water tank 11. Water in a water supplying tank 15 passes through a pipe 16 connecting the water supplying tank 15 with the inner water tank 11 and then water is supplied to the inner water tank 11 by a water supplying pump 17 driven by an electric motor.