A photoelectric conversion element comprises: a plurality of pixels, each of which performs photoelectric conversion and outputs an analog signal; an analog processing unit that sequentially processes, on a pixel-to-pixel basis, the analog signals output from a pixel group including the pixels; and a signal supply unit that supplies a signal needed for preliminary operation to the analog processing unit so as to enable the analog processing unit to perform the preliminary operation before the analog processing unit starts to process the analog signals output from the pixel group.