A shared-pixel-type image sensor includes a semiconductor substrate, four photoelectric conversion elements disposed adjacent to one another in one direction on the semiconductor substrate, two first transmission elements transmitting charges accumulated in two adjacent ones of the photoelectric conversion elements to a first floating diffusion region, respectively, two second transmission elements transmitting charges accumulated in the other two adjacent photoelectric conversion elements to a second floating diffusion region electrically coupled with the first floating diffusion region, respectively, MOS capacitors that are electrically coupled with the first or second floating diffusion region, a reset element resetting the charges of the first and second floating diffusion regions to a reference value, and a drive element and an select element outputting the charges of the first or second floating diffusion region.