An image sensor includes a pixel group. The pixel group includes a first color filter, first to third photodiodes below the first color filter such that the first color filter overlaps each of the first to third third photodiodes in a vertical direction, wherein the first to third photodiodes are arranged in a first direction perpendicular to the vertical direction, first to third floating diffusions configured to accumulate electric charges generated by the first to third photodiodes, respectively, a source follower transistor configured to output a first pixel signal based on the electric charges accumulated in at least one of the first to third floating diffusions, and a first metal layer configured to receive the first pixel signal from the source follower transistor, wherein the first metal layer extends in a second direction intersecting the first direction, wherein the first to third floating diffusions are arranged in the first direction.