PURPOSE: To approve an image on the front of photographic paper and to observe printed information on its back by providing a means which displays the back of the photographic paper near a base through the light transmitting part of the testing base.

CONSTITUTION: After a frame number and exposure information are printed on the back of the photographic paper 14, it is carried to a winding part 20 from a supply part 16. The lower part of a testing part 36 is the testing base 37, and its part facing each print area on the back of the photographic paper is provided with rectangular holes 39A and 39B, which transmits light reflected on the back. The light is observed by a combination of reflecting mirrors through an upper rectangular hole 43, and its image is formed on a screen provided on the hole 43 through a lens, or the image is photographed by a camera to display the image on the display of the hole 43, thereby detecting the surface image. Simultaneously, information on the back of the photographic paper is detected, and average density in the area of compared with a reference value, whereby the matching of the information with the surface image position can be detected.