PURPOSE: To stably travel an original platen when performing exposure and to quickly return the original platen when the exposure is completed with an inexpensive mechanism by providing a spring with a tensile force lower than driving torque when energizing a driving motor and higher than holding torque when de-energizing it.

CONSTITUTION: The driving motor 5 is energized when the exposure is performed, and when the original platen is moved in a scanning direction and the exposure is completed, a current is cut off. Here, the spiral spring 10 with the tensile forced lower than the driving torque when energizing the motor 5 and higher than the holding torque when no current flows is provided, and the tensile force is set so as to function on the original platen in a direction opposite to the scanning direction. Therefore, at a moment when the current of the motor 5 is cut off, the original platen 2 is quickly returned to an exposure start position. Thereby, it is possible to stably obtain the travel of the original platen glass 2 when performing the exposure with an inexpensive and simplified mechanism, and to quickly return the original platen glass 2 to a home position.