An air purifier according to the present invention comprises: a case having an inlet formed to suction external air; a primary purification part provided inside the case so as to purify the suctioned air; and a discharge part formed at the upper portion of the primary purification part so as to discharge the purified air. Therefore, the primary purification part comprises: a purification part for purifying the external air; a cleaning part for cleaning a filter; and a sterilization part for sterilizing the cleaned filter, and thus can perform purification, cleaning, and sterilization, simultaneously, so that a purification operation can be performed at industrial sites without stopping.