PURPOSE: To provide the method for correcting a dark state output of an image sensor reducing dispersion in a dark state output in order to prevent deterioration in the image quality due to the dispersion in the dark state output of the image sensor.

CONSTITUTION: A counter circuit 41 whose count corresponds to the bit number for dark state output correction is counted synchronously with a bit output clock. a digital output of the counter circuit 41 is D/A-converted and a resulting analog signal is fed to a differential amplifier 44. The differential amplifier 44 subtracts an analog signal obtained by D/A-converting a digital output of the counter circuit 41 from a picture read output (analog signal) of a sensor 45 corresponding to each bit to obtain a picture read output (analog signal) of a sensor 45 to be corrected. Thus, in the image sensor where its dark output level is almost uniformly changed corresponding to a time series and a picture element string, a dark state output is corrected without loss of digital resolution and without use of expensive circuit configuration.