A humidifying air purifier includes a body frame having an opened front and rear, a fan housing coupled to a rear end of the body frame and having a fan intake, a housing cover coupled to a rear end of the fan housing to accommodate an air blowing fan, and an air discharge port formed at an upper end of the fan housing and an upper end of the housing cover. A waterwheel motor is installed on a front surface of the fan housing and positioned outside the fan intake, a driving gear is coupled to the waterwheel motor, a door assembly is configured to be pushed into or drawn out from a front end of the body frame, a water tub is accommodated in a lower side of the door assembly, and a humidifying filter assembly is inserted into the water tub.