The invention provides a solid state imaging device and imaging system, both capable of obtaining a good image suppressing the reduction of the SN ratio thereof, suppressing the increase of the chip size of the imaging device and suppressing the increase of power consumption of a sensor without performing complicated processing even if there are regions different in luminance mutually in an imaging plane. Variable gain units provided correspondingly to columns of pixels amplify the signals from the pixels by different gains group by group of the pixels each group including a plurality of pixels according to the signals from the outside.