To decrease a step difference in the signal and to make the linearity characteristics of respective output channels coincide in an image sensor adopting the left right division read system.

The image pickup device is provided with a color linear image sensor adopting left right dividing read system, a plurality of signal processing means (1-12) that apply prescribed signal processing to image signals outputted from each output terminal of the color linear image sensor, a white board (210), a gray reference board (701), a CPU (20) that obtains adjustment data that nearly matches the level of an image signal of the white board with a 1st prescribed level, the level of the image signal of the gray reference board with a 2nd prescribed level, and adjusts a level of the image signal corresponding to another gray scale to the level obtained by interpolating the level between the 1st and 2nd prescribed levels and LUTs (13-16) that are used to adjust the image signals outputted from a plurality of the corresponding signal processing means.