A humidifier includes a water tank for containing a predetermined amount of water, a supporting base having a water chamber, a mist discharging channel, a mist generating module for generating a mist from the water in the water chamber and generating an air flow, and a noise reduction air duct. The noise reduction air duct has an air inlet extended from the water chamber for receiving the air flow and the mist, an air outlet extended to the mist discharging channel, and a detouring channel extended between the air inlet and the air outlet for detouring a direction of the mist from the water chamber to the mist discharging channel so as to reduce a speed of the mist for noise reduction.