To provide a compact system having the improved lateral merging of a two-up printed sheet, capable of selecting image input to a substrate more flexibly

This system concurrently prints a double page image on double image substrates arranged side by side as a pair across the direction of a printing passage 11 laterally, so as to raise a throughput printing speed. In this system, an electron image forming system 30 to print two different page images on sheets 18a and 18b as a pair, and sheets 12a and 12b are laterally shifted along the upper ends thereof and overlapped on top of each other. In addition, the system includes an output sheet lateral merging system 40 and a stacking system 50 for stacking continuous and overlapped sheet pairs on top of each other and providing collated pre-cut copy sheets after the two-up printing.