PURPOSE: To enable the positions of two pictures on the obverse and the reverse of a paper to reliably coincide with each other, by a method wherein, in a device which accumulates a recording paper, wherein recording of a picture on the first surface is completed, in order to record a picture on the second surface, a means which displaces the position of the accumulated papers is mounted.

CONSTITUTION: A paper sheet P, in which recording of a picture on the first surface 1 is completed, is turned over by a turn over part R, carried by a carry belt 11, and accumulated on a paper accumulating plate 12 with its first surface down. When duplication of a given number of paper sheets is completed, the accumulated paper sheets are delivered one by one to the following process by means of a sheet feed roller 16, and recording of a picture on the second surface is effected. In which case, both side plates 13 and 13', which control and displace the accumulating position of the paper sheets, are mounted on the paper sheet accumulating plate 12, the side plates are driven by motors 14 and 14', and the positions are detected by sensors 15. In this constitution, the both side plates 13 and 13' are simultaneously moved in the same direction by a specified distance for displacement, and this causes the picture on the obverse of the paper sheet to reliably coincide with the position on the reverse of the paper sheet.