A photoelectric conversion device includes a plurality of pixels, a plurality of output lines, to which signals from corresponding pixels are output, respectively, an amplification unit arranged corresponding to each of the plurality of output lines and configured to amplify a signal output to a corresponding output line, a comparison unit arranged corresponding to each of the plurality of output lines and having a first input terminal and a second input terminal, a signal corresponding to an output of the amplification unit being input to the first input terminal, a reference signal being input to the second input terminal, and a switch connecting nodes of the plurality of output lines. During a period before an offset clamping operation is completed, the switch is turned on.