Improvement of conversion precision in an analog-to-digital converter is realized. Therefore, a voltage of a correction signal and a voltage obtained by attenuating the voltage with a fixed attenuation rate by an attenuation circuit 21 are generated and each voltage is input to an analog-to-digital conversion unit 23. A correction unit 20a receives a digital output from the analog-to-digital conversion unit 23, searches a correction coefficient Wi of each bit of the analog-to-digital conversion unit 23, based on an adaptive control algorithm, and corrects the digital output from the analog-to-digital conversion unit 23 using the searched correction coefficient Wi.