An image capturing apparatus includes a light receiving sensor including two-dimensionally arranged pixels and configured to photoelectrically convert a pair of object images and to output a first image signal and a second image signal, each of the first image signal and the second image signal corresponding to a respective object image of the pair of object images; a calculation unit configured to calculate a first phase difference between the first image signal and the second image signal in the first direction and a second phase difference in a second direction; a focus detection unit configured to calculate a first focus detection result based on the first phase difference; and a determination unit configured to determine presence or absence of heat haze based on the second phase difference.