An image sensor including a color filter array layer, which includes a plurality of color filters transmitting light of different colors; and reflective partitioning walls, which define the color filters and have a lower refractive index than that of the color filters; a color separation device, which separates incident light into a plurality of colors, such that the plurality colors are incident on the plurality of color filters, respectively; and a sensor substrate, on which a plurality of light detection devices for respectively sensing light transmitted through the plurality of color filters are arranged in an array shape.