A polarization image sensor includes: photodiodes arranged on an image capturing plane; a color mosaic filter in which color filters in multiple different colors are arranged to face the photodiodes; an optical low-pass filter which covers the color mosaic filter; and polarization optical elements located closer to a light source than the optical low-pass filter is. Each polarization optical element covers an associated one of the photodiodes and makes light which is polarized in a predetermined direction in a plane that is parallel to the image capturing plane incident onto the optical low-pass filter. The color filters are arranged so that light that has passed through polarization optical elements is transmitted through an associated one of the color filters in a single color. Each color filter covers multiple photodiodes.