A solid-state imaging device includes a plurality of pixels disposed in a two-dimensional array that individually output analog pixel signals corresponding to amounts of light received thereat, a vertical scanning circuit that selects a pixel row, vertical signal lines each installed in correspondence to a pixel column, through which the pixel signals output from pixels belonging to the row selected by the vertical scanning circuit are transmitted, a horizontal scanning circuit that selects a plurality of pixel columns simultaneously, a composition circuit that combines pixel signals corresponding to the columns selected simultaneously by the horizontal scanning circuit, among the pixel signals output to the vertical signal lines, a first conversion circuit that converts the analog composite pixel signal generated at the composition circuit to a digital signal and a horizontal signal line through which the pixel signal digitized at the first conversion circuit is transmitted.