An image forming apparatus contains a transporting unit for transporting a sheet of paper to an image forming section, a deviation detection sensor which detects a passing position of the transported sheets of paper and outputs passing data of the transported sheets of paper for every sheet of paper, a deviation calculation section which generates deviation storage data for evaluating a condition of a transporting section or a detection section by performing statistical processing on the passing data of the transported sheets of paper, and a discrimination section which discriminates between a case in which there is malfunction in the transporting section and a case in which there is malfunction in the detection section by comparing the deviation storage data with deviation characteristics data for discriminating between the malfunction in the transporting section and the malfunction in the detection section.
