The present disclosure discloses a humidification device, a humidifier and a ventilator, overcoming the deficiency that when the structure of a water tank of a current ventilator causes the water tank to tilt or sway, it is easy for a large amount of water to enter a heating portion. The humidification device comprises a heating portion and a liquid inlet structure adding liquid to the heating portion. The heating portion comprises an accommodating chamber and a transition chamber limiting the amount of liquid in the accommodating chamber, and the liquid inlet structure is communicated with the transition chamber and allows the liquid to enter the transition chamber. According to embodiments of the present disclosure, a large amount of stored water may be prevented from entering the heating portion and thus affecting the heating efficiency when a water tank or a similar humidification device tilts.