a plurality of pixels which are one-dimensionally or two-dimensionally arranged and output photoelectrically converted signals;

a plurality of output lines to which the output signals from the pixels are outputted;

a plurality of amplifiers connected to said plurality of output lines, respectively, configured to amplify the output signals from the pixels with a gain exceeding 1;

an adder circuit having a plurality of first switches configured to select output signals from the plurality of amplifiers, and output added selected output signals;

an output circuit having a plurality of second switches each having one terminal connected to an output terminal of one of the amplifiers, and outputting output signals from the plurality of amplifiers without adding;

a reading circuit configured to read out signals outputted from the adder circuit and the output circuit; and

an output amplifier configured to output signals read out by the reading circuit,

wherein the adder circuit further comprises a plurality of storage capacitors each having one terminal connected to each of the first switches, wherein the other terminals of the storage capacitors are connected commonly,

wherein the reading circuit further comprises a third switch connected between the storage capacitors and the output amplifier, and a fourth switch connected between the other terminal of the second switch and the output amplifier, and

wherein the second switch is turned off while said adder circuit outputs added signals, and the first switch is turned off while said output circuit outputs output signals from the plurality of amplifiers without adding.