1. A focus control apparatus for detecting a phase difference between two images to acquire defocus information, comprising at least one processor or one circuitry which functions as: an acquiring unit which acquires first defocus information by detecting a phase difference between two images in a first direction 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 by detecting a phase difference between two images in the first direction 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 both the first defocus information acquired based on the output of the image sensor corresponding to the first region and the second defocus information acquired based on the output of the image sensor corresponding to the second region, and performs focus control based on the obtained defocus information, wherein the first region has a length longer than the length of the second region in the first direction.