An image forming apparatus includes a reading unit reading an original document and generating image data; a power source unit supplying power to the reading unit; a power source switching signal output unit outputting a switching signal for switching between supply and shut-off of the power for any one of an image pickup element and an image processing unit; a measuring unit measuring a power stopping time while the power is shut off; a judging unit determining whether to carry out only a first initial setting when the measured power stopping time is less than a predetermined time and whether to carry out both the first initial setting and a second initial setting when the measured power stopping time is the predetermined time or more; and an initial setting unit carrying out only the first initial setting or the second initial setting also upon the determination by the judging unit.