a magnification factor a preferential paper selection function in which a previously memorized paper size is selected and a manual paper selection function in which a preferred paper size is selected by a key manipulation these three paper selection functions are called for by manipulation of the key in succession and in rotation application_number US 15254688 A description fig1 is a schematic structural arrangement view of a copier machine fitted with a preferred embodiment of the paper size selection apparatus of the present invention in this drawing numeral 1 represents a machine main body and 2 denotes generally a scanning system which is adapted for transmitting optical images provided by conventional exposure operation of a document and is positioned within the interior space of the main machine body 1 the scanning system 2 comprises an exposure lamp 20 first mirror 21 second mirror 22 third mirror 23 fourth mirror 24 magnification factor setting lens 25 and the like numerals 3 represents an image formation system for reforming the images transmitted from the scanning system 2 on the paper through the way of electrophotographing process comprising a photosensitive drum 30 a developing unit 31 a charger 33 a main eraser 34 a cleaning blade 35 separation.