In a printing method using an ink jet head, a chemical liquid may be discharged onto a substrate from a plurality of nozzles of the ink jet head. Discharging numbers of the chemical liquid from the plurality of nozzles may be identified and a cumulative discharging number of the chemical liquid from the plurality of nozzles may be calculated. The cumulative discharging number of the chemical liquid may be compared with a previously set limit discharging number of the ink jet head. A replacement time of the ink jet head may be determined if the cumulative discharging number of the chemical liquid exceeds the previously set limit discharging number.