To save the time and forms for operation for confirming whether or not adjustment values are proper by forming a test image and to perform the operation more accurately and efficiently by deciding which register means an adjustment value of image positioning timing is concerned in and selecting corresponding forms for a tray as an object of paper feeding.

When the depression of a start key is confirmed (S4) and the adjustment of a 1st register is judged (S5), a 1st tray is automatically selected (S6) as an object tray of paper feeding and test printing based upon paper feeding from the 1st tray is started (S7). When it is judged that the adjustment is the adjustment of a 2nd register (S5), a 2nd tray is automatically selected as an object tray of paper feeding (S9) on condition that the 2nd tray is usable, but when the 2nd tray is unusable, on the other hand, a 3rd tray is automatically selected as an object tray of paper feeding (S10).