PURPOSE: To suppress the generation of false red signals and to improve the picture quality of a read image at the two-color (white/black and red) original reader equipped with two light sources.

CONSTITUTION: Two reference voltages E2 and E3 (E3>E2) are prepared as the reference voltages of the binary comparator of a binarizing circuit 1 to convert analog image signals (completing the analog processings of clamp and S/H or the like) obtained from an imaging device such as a CCD, etc., to digital signals, and these reference voltages E2 and E3 are suitably switched according to a control signal inputted to a selecting circuit 4. The above-mentioned control signal is generated according to control logic so as to be changed synchronously to the timing of scanning respective charges stored in the light sources of the two colors. At the two-color original reader, the picture quality of read images can be improved by suppressing the generation of the false color (red) signals.