A preprocessor converts an analog image signal, which is outputted from a solid-state image pickup sensor that photoelectric-converts an optical image of a subject, into digital image data. A timing generator periodically generates a drive pulse for driving the solid-state image pickup sensor continuously/discontinuously, and generates an output stop position signal that indicates an output stop position of the solid-state image pickup sensor when the solid-state image pickup sensor is driven discontinuously in sync with the drive pulse. A continuous data generator lets through the image data when the output stop position signal is invalid, and converts the image data inputted in a discontinuous state into continuous image data when the output stop position signal is valid.