A solid-state image sensor includes a pixel array unit including a plurality of pixels arranged in the form of an array, column signal lines adapted to transmit pixel signals output from pixels in respective columns, a noise adding unit adapted to add temporally constant and two-dimensional spatially random noise to the pixel signals transmitted via the column signal lines, and an analog-to-digital converter adapted to convert a signal level and a reference level of each pixel signal including the noise added thereto by the noise adding unit.