PURPOSE: To improve reading accuracy for an original facing upward and to facilitate assembly and adjustment by uniformly applying pressure to a transparent plate with the aid of air pressure when a sealed small chamber in which the original is placed is decompressed and making to adhere the original surface to the transparent plate uniformly.

CONSTITUTION: A glass plate 2 is opened in a direction a, and the original 20 is placed on an original placing table with its face turning upward. The glass plate 2 is closed in a direction B, and an upper/lower adjusting part 11 is moved vertically to slightly push the front surface of the original 20 to the glass plate 2. At this time, the tip of adsorbing member 4 is adjusted to come into contact with the bottom of the glass plate 2. A suction part 12 is operated to discharge the air in the small chamber 3 from suction ports 7C and 7D. Since air pressure is uniformly applied to the glass plate 2 in a direction P, the original 20 is pushed to the surface of the glass plate 2 with uniform pressure.