PURPOSE: To conduct adjustment having high accuracy in a short time by comparing a measured value by a sensor at the time of adjustment, a previously stored specification and a tolerance, deciding nondefective/defective and displaying, outputting and recording the result.

CONSTITUTION: When each section is adjusted, each section is started from a maintenance panel 12, and a signal (a measured value) acquired by a sensor 6 while performing actual printing operation is converted into a digital value, which can be processed, by a main control CPU circuit 8 by a printer-mechanism drive monitor circuit 10. A converted value is transmitted over the CPU circuit through a printer control circuit 9. In the CPU circuit, a specification corresponding to a measured value and a tolerance are read from a non-volatile recorder 11, and compared with the measured value and a nondefective or a defective is decided, and the result of the decision is output to an indicator on the maintenance panel 12 together with the measured value, the specification and the tolerance. The validity of the measured value by the sensor at a time when such a device is operated actually can be decided on the readjustment of the device, and self-diagnosis is conducted easily.