An image reading apparatus comprises a first reading unit configured to output an analog signal by reading an original, a second reading unit different from the first reading unit, a conversion unit configured to convert analog signals outputted from the first reading unit and the second reading unit to digital signals, a wire connection control unit configured to control wire connection between the first reading unit and the second reading unit, and the conversion unit, and an output control unit configured to control an output of an analog signal from the first reading unit.