A solid-state imaging device includes a pixel array section and a signal processing section. The pixel array section is configured to include a plurality of arranged unit pixels, each of which is a rectangular pixel having different sizes in the vertical and horizontal directions, and a plurality of adjacent ones of which are combined to form a square pixel having the same size in the vertical and horizontal directions. The signal processing section is configured to process a plurality of signals read out from the combined plurality of unit pixels and to output the processed signals as a single signal.