1. A focus control apparatus for detecting a phase difference between two images to acquire defocus information, comprising: an acquiring unit which acquires first defocus information based on an output of an image sensor corresponding to a first region in an area of a captured image, and acquires second defocus information based on an output of the image sensor corresponding to a second region in the area; and a control unit which obtains defocus information corresponding to the area using the first defocus information and the second defocus information, and performs focus control based on the obtained defocus information, wherein the first region has a length longer in a phase-difference detection direction than the length of the second region.