A solid-state imaging apparatus comprising a plurality of pixels generating a photoelectric conversion signal, a column amplifying unit corresponding to columns of the pixels, for outputting a first and second signals generated by amplifying the photoelectric conversion signal at a smaller first gain and larger second gain respectively, an analog to digital converter (21) for converting the first and second signals from an analog signal to a digital signal, a comparing unit (224) for inputting the digital signal from the analog to digital converter, level-shifting into the same gain level the first and second signals converted by the analog to digital converter, and thereafter detecting a gain error between the level-shifted first and second signals, and a correction unit (226) for correcting the first and second signals based on the gain error.