PURPOSE: To decrease a mounting space for a detector and easily perform its wiring and mounting work, by providing two actuators, which can mutually and independently drive the detector, to a single of the detector and obtaining a desired detection signal from the single detector.

CONSTITUTION: The first actuator 21 is pivotally mounted turnably to a strut 24 under a document table 1, and one end part 21a of the actuator 21 is protruded from the table 1 in the vicinity of the first roller 2, while the other end part 21b is positioned in a light path 23a of an optical sensor 23 when the one end part 21a is not pressed by a document 25 and retreated from the light path 23a when said part 21a is pressed. While the second actuator 22 is pivotally mounted turnably to a strut 26 under the table 1, and its one end part 22a is protruded from the table 1 between the first roller 2 and exposure window 3, then the other end part 22b is positioned in the outer of the light path 23a of the optical sensor 23 when the one end part 22a is not pressed by the document 25 while retreated from the outer of the light path 23a of the sensor 23 after once crossing the light path 23a when said part 22a is pressed. In this way, a desired signal from the optical sensor 23 can be obtained.