An apparatus prepares a mounting sheet of originals upon which are drawn the original positioning or arrangement lines and an area to be trimmed. When originals are pasted on the sheet and scanned by a scanner, the picture data of an original is read out. In this apparatus, a magnification, a position and a direction of an original can be entered or inputted on a data tablet and in response to the input data, a mounting sheet is automatically prepared. An operator pastes a original along the original positioning or arrangement lines on the mounting sheet and a picture in the trimmed area is scanned. Furthermore, the apparatus automatically selects an optimum drum of a scanner depending upon the magnification of each original.