When signal charges are read from light receiving pixels of each of CCD sensors, which are arrayed linearly such that end regions of CCD sensors adjacent to each other overlap with respect to a direction intersecting with the linear array direction of the CCD sensors, binning processing of the signal charges is performed, such that a position of one unit of light receiving pixels, which are to be subjected together to the binning processing, at the end region of one of the CCD sensors adjacent to each other and a position of one unit of light receiving pixels, which are to be subjected together to the binning processing, at the end region of the other CCD sensor coincide with each other with respect to the linear array direction of the CCD sensors.