An image sensor includes photoelectric conversion elements formed adjacent to each other on a substrate. Two transmission elements transmit charge accumulated in two adjacent photoelectric conversion elements to a first floating diffusion region, and another two transmission elements transmit charge accumulated in the other two photoelectric conversion elements to a second floating diffusion region. The first floating diffusion region is electrically connected to the second floating diffusion region. A plurality of readout elements read out the charge transmitted to the first and the second floating diffusion regions. The image sensor also includes a dummy gate group including at least one dummy gate arrayed substantially parallel to a readout gate of the plurality of readout elements.