A focus detecting apparatus includes an acquisition unit configured to acquire a defocus amount using a pair of image signals corresponding to each of a first focus detecting area and a second focus detecting area larger than the first focus detecting area set for each of the plurality of AF frames, a determination unit configured to determine a priority of the plurality of AF frames using the pair of image signals acquired from each of the first and second focus detecting areas, and a selection unit configured to select the AF frame to be focused using the priority.