To shorten self-diagnosis time at the time of turn on of power while ensuring reliability of an apparatus by grasping the state of each device on the apparatus in view point of self-diagnosis thereby performing necessary and sufficient self-diagnosis at all times.

When a device error occurs, or the software version is different from that at the time of previous turn-on power, or an optical device is different from that at the time of previous turn-on power, a printer controller 100 performs self-diagnosis different from normal one in detail every time when power is turned on. Consequently, reliability of self-diagnosis function can be ensured while shortening self-diagnosis time.