the change of the direction of placement of the original document at n7 next the magnification ratio is set 4d at n8 which is followed by n11 in the case where the size of the original document is detected not to be a4 in n4 the flow advance to n5 where it is determined whether or not the size of the original document is b4 if the original document placed on the platform is determined to be b4 in n5 the flow proceeds to n9 where the magnification ratio is selected to be 33 and then to n11 on the contrary if the size of the original document placed on the platform is decided not to be b4 at n5 then the size of the original document is determined to be b5 and the flow starts to n10 where the magnification ratio is changed to be 4d succeeding to n11 when the original document of a3 size is selected in the aforementioned process a magnification ratio is selected in accordance with the detected size of the original document in the case that the set size of the copy paper is not a3 at n1 the flow goes to n17 where it is detected whether or not the size of copy paper set by the operator is a4 if the set size of the copy paper is a4 n17 is succeeded by n18 when the size of the original document placed on the platform is a3 a copy paper cassette in which copy paper of a4 size are placed with their longitudinal direction parallel to the direction of supply of copy paper is selected in n19 and the magnification ratio is set 06 at n22 thereafter the flow continues.