In FIG. 6A, a sheet P having a crease 70 in which a steeply inclined surface 72 is formed on a first side DirL in the sub-scanning direction DM and a gently inclined surface 74 is formed on a second side DirR in first sheet reading is drawn. In second sheet reading, since the sheet P is rotated from the first sheet reading, as illustrated in FIG. 6B, the gently inclined surface 74 is disposed on the first side DirL in the sub-scanning direction DM, and the steeply inclined surface 72 is disposed on the second side DirR in the sub-scanning direction DM. The position of the crease 70 to be specified in FIGS. 6A and 6B is a position β on the right side of the steeply inclined surface 72 in FIG. 6A (a position on the second side DirR in the sub-scanning direction DM), and a position β on the left side of the steeply inclined surface 72 in FIG. 6B (a position on the first side DirL in the sub-scanning direction DM).
