A photoelectric conversion apparatus comprising: a plurality of pixels provided in a plurality of columns; a reference signal generating unit configured to generate a first reference signal and a second reference signal, the first reference signal having a first changing rate with respect to time, and the second reference signal having a second changing rate with respect to time, wherein the first changing rate is smaller than the second changing rate; a plurality of analog-to-digital conversion units (30, 40, 30-1, 40-1) each provided for a corresponding one of the plurality of columns, each of the plurality of analog-to-digital conversion units (30, 40, 30-1, 40-1) being configured to convert a signal of a corresponding one of the plurality of pixels into a digital signal by comparing the signal and one of the first reference signal and the second reference signal; characterized by: a correction unit (50, 40-1) configured to correct the digital signals based on an error between a ratio of the first changing rate and the second changing rate and a desired ratio of the first changing rate and the second changing rate, wherein the correction unit (50, 40-1) is configured to correct the digital signal in accordance with respective digital signals obtained by comparing a first analog signal having a first level and the first reference signal, comparing the first analog signal having the first level and the second reference signal, comparing a second analog signal having a second level and the first reference signal, and comparing the second analog signal having the second level and the second reference signal. a plurality of pixels provided in a plurality of columns; a reference signal generating unit configured to generate a first reference signal and a second reference signal, the first reference signal having a first changing rate with respect to time, and the second reference signal having a second changing rate with respect to time, wherein the first changing rate is smaller than the second changing rate; a plurality of analog-to-digital conversion units (30, 40, 30-1, 40-1) each provided for a corresponding one of the plurality of columns, each of the plurality of analog-to-digital conversion units (30, 40, 30-1, 40-1) being configured to convert a signal of a corresponding one of the plurality of pixels into a digital signal by comparing the signal and one of the first reference signal and the second reference signal; characterized by: a correction unit (50, 40-1) configured to correct the digital signals based on an error between a ratio of the first changing rate and the second changing rate and a desired ratio of the first changing rate and the second changing rate, wherein the correction unit (50, 40-1) is configured to correct the digital signal in accordance with respective digital signals obtained by comparing a first analog signal having a first level and the first reference signal, comparing the first analog signal having the first level and the second reference signal, comparing a second analog signal having a second level and the first reference signal, and comparing the second analog signal having the second level and the second reference signal. a correction unit (50, 40-1) configured to correct the digital signals based on an error between a ratio of the first changing rate and the second changing rate and a desired ratio of the first changing rate and the second changing rate, wherein the correction unit (50, 40-1) is configured to correct the digital signal in accordance with respective digital signals obtained by comparing a first analog signal having a first level and the first reference signal, comparing the first analog signal having the first level and the second reference signal, comparing a second analog signal having a second level and the first reference signal, and comparing the second analog signal having the second level and the second reference signal.