Provided is a photoelectric conversion apparatus including: a pixel array having pixels arranged in matrix; a pixel output line provided according to each column of the pixel array and transmitting a pixel signal output from a pixel of each column of the pixel array; a column signal processing unit provided according to each column of the pixel array and into which the pixel signal is input from the pixel output line, in which the column signal processing unit has a plurality of horizontal adding up or averaging units configured to add up or average the plurality of pixel signals based on the pixels of different columns of the pixel array; and a plurality of adding up or averaging modes with different numbers of columns subjected to adding up or averaging can be selected by selectively using one or a plurality of the plurality of horizontal adding up or averaging units.