Incidentally, e is a value determined the size of the sheet conveyed: (L???v??+w)/V<(L???v?????K)/v???(1) [0161] Further, by forming the minimum plus sheet interval w in this way, although the detecting sensor 60 can detect the leading end of the sheet, since the minimum sheet distance w is formed between the first and second roller pairs, as shown in FIG. 17, the detecting sensor 60 is positioned