PURPOSE: To make effective inspection work for prevention of recurrence by furnishing a display means to display the name of a sensor or corresponding code part, in which the data selected by a data comparing/selecting means is assumed.

CONSTITUTION: When out-of-alignment state from sensors 5 is sensed, the out-of- alignment data according to the situation is compared by a comparing/selecting part 8 at each applicable time with the inconvenience data generated when an inconvenient state of each sensor 5 is assumed, and the data which is in the best agreement shall be selected. Then the name of sensor or corresponding code part, in which this selected data is assumed, will be displayed on a display device 10. This allows effective performance of proper inspecting work for prevention of recurrence.