Provided are an image sensor and an image capturing apparatus including the image sensor. The image sensor includes a pixel array including: multiple sensing pixels outputting image signals respectively corresponding to intensities of incident light; and at least one pair of focusing pixels that are adjacent each other, and each outputting a phase difference of the incident light as a focusing signal; wherein each focusing pixel includes: a semiconductor layer including a photodetecting device accumulating electric charges generated according to absorbed light from among the incident light; a wiring layer formed on a first surface of the semiconductor layer and including wirings; a planarization layer having a first surface on a second surface of the semiconductor layer; a shielding layer formed in the planarization layer to block some of the incident light to be incident to the photodetecting device; and a color filter layer and a micro lens layer.