An image pickup apparatus including: a plurality of photoelectric conversion elements for photoelectrically converting light from an object, a first output line to which signals from the plurality of photoelectric conversion elements are successively outputted, a plurality of first switches connected to the first output line to output the signals from the plurality of photoelectric conversion elements to the first output line, a second output line to which a reference signal is supplied, a plurality of second switches connected to the second output line to supply the reference signal to the second output line, a scanning circuit which controls the plurality of first switches and the plurality of second switches, and a differential circuit which obtains a difference between the signal from the first output line and the signal from the second output line.