A distance detection apparatus includes a calculation unit configured to detect an object distance to an object based on a first signal formed by a luminous flux that has passed through a first pupil area of an imaging optical system and a second signal formed by a luminous flux that has passed through a second pupil area of the imaging optical system different from the first pupil area, which are generated by using an image sensing unit including multiple pixels. The calculation unit performs a first process for calculating one of a defocus amount and the object distance by a phase difference method based on the first signal and the second signal and a second process for calculating one of the defocus amount and the object distance by a depth-from-defocus (DFD) method based on the first signal and the second signal.