An image pickup apparatus comprising a pixel configured to convert optical signal into an electrical signal, a comparison unit configured to compare a pixel signal from the pixel with a reference voltage, an A/D conversion unit configured to analog/digital (A/D)-convert the pixel signal in a conversion mode selected based on a comparison result of the comparison unit, and a correction unit configured to correct at least one of an offset and a gain generated by the A/D conversion for an output data of the A/D conversion unit, wherein a value for offset correction or gain correction performed by the correction unit is changed according to the selected conversion mode.