A depth measurement apparatus including ranging pixels each having a plurality of photoelectric conversion units for receiving light fluxes that have respectively passed through first and second pupil regions, a reading unit that is shared by the plurality of photoelectric conversion units, and a control unit for controlling the ranging operation, wherein a signal charge accumulated in one of the photoelectric conversion units is output as a first signal and a second signal obtained by adding a signal accumulated in the other photoelectric conversion unit to the first signal is output, the signal charge accumulated in the other photoelectric conversion unit is acquired based on a difference between the first and second signals, and the signal charge of the photoelectric conversion unit receiving flux with a lower transmittance is read first.