An inkjet image forming apparatus includes a print head, an ink supply unit, an ink supply flow path connecting the ink supply unit and the print head, an ink supply amount detector which detects the amount of ink supplied through the ink supply flow path, and a controller which controls a maintenance operation of the print head according to the amount of supplied ink detected by the ink supply amount detector. The controller determines the states of nozzles of the print head according to the amount of supplied ink and cleans the nozzles using supersonic waves or performs wiping and spitting of the nozzles, thereby achieving efficient maintenance.