An imaging device includes a pixel region in which light sensing pixels are grouped into pixel-units that each include multiple pixels, each column including pixels from at least two of the pixel-units. Each of the pixel-units is connected, via a corresponding readout line, to a corresponding readout unit configured to perform analog-to-digital conversion on pixel signals output thereto. A scanning unit that extends in a column direction is configured to select pixels for readout by applying row scanning pulses to scan lines connected to rows. A scanning unit that extends in a row direction for applying readout-enabling scan pulses to lines connected to columns is omitted. Those pixels that are selected for readout by one of the row scanning pulses are read out independently of any enabling pulses applied to lines connected to columns.