To reduce the entire device without giving effects on conditions such as placing of an original while reducing a shading correction of the device by realizing shading correction in the subscanning direction with numerical control.

The device has a subscanning direction counter 18 that generates a subscanning direction address signal denoting a read scanning position in the subscanning direction, a subscanning direction shading correction register 22 that stores correction used for correcting a subscanning direction shading characteristic at a read scanning position, a PWM signal generating section 25 that generates a luminance control signal in response to a read scanning position from a subscanning direction address signal, and a lamp drive section 28 that controls luminance of a lamp 35 based on a luminance control signal.