A solid-state image pickup apparatus includes pixels arranged in a matrix, each pixel converting incident light into an analog electrical signal and outputting the analog electrical signal; AD converters in correspondence with individual columns, each AD converter converting the analog electrical signal from a corresponding pixel into a digital signal and outputting the digital signal from an output terminal; register circuits in correspondence with the individual columns, each register circuit receiving at an input terminal the digital signal output from the output terminal of a corresponding AD converter and storing the digital signal; and connection units, each of which connects the output terminal of a corresponding AD converter for one column to the input terminal of a corresponding register circuit for a different column or to connect the output terminal of a corresponding register circuit for one column to the input terminal of a corresponding register circuit for a different column.