A ranging apparatus capable of suppressing reduction of ranging accuracy at a long distance end of a distance measurement range, thereby making it possible to perform high-accuracy ranging over a wide distance range. An image pickup device receives light fluxes from a fixed focus optical system. A distance information acquisition unit acquires distance information of an object based on image signals from the image pickup device. This section acquires the distance information based on parallax between a first image based on a light flux having passed a first region of an exit pupil, and a second image based on a light flux having passed a second region of the exit pupil. The optical system is configured such that parallax of an object existing at a predetermined distance is smaller than parallax of an object existing at a shorter distance than the predetermined distance.