To allow obtaining an image with a stable black level in a real time by detecting an offset voltage of a photoelectric conversion circuit at every line.

This input device light receives light from a sample obtained by optically two-dimensionally scanning the sample with the photoelectric conversion circuit 31, converts it to a luminance signal, image processes the luminance signal and gains the information of the sample image. At this point, the correction amount of the black level of the image is detected from a signal incorporated in the output of the photoelectric conversion circuit 31 by using the part that the light from the sample isn't made incident on the photoelectric conversion circuit 31 in a scanning period, and the luminance signal is corrected, based on the detected correction amount.