The humidifier includes a humidifying member, a storage water tank, a circulating water tank, a residual water tank, a supply pump configured to supply water accommodated in the storage water tank to the circulating water tank, a circulating pump configured to supply water accommodated in the circulating water tank to the humidifying member. A fan configured to blow air toward the humidifying member and thereby cause water evaporated to be discharged outside the humidifier, an internal pipe configured to form a flow passage through which water not evaporated by the humidifying member is recovered to the circulating water tank, a drainage member configured to selectively discharge water accommodated in the circulating water tank to the residual water tank, and a controller configured to operate the humidifier in humidity mode based on the water level in the storage water tank.