A depth measurement apparatus including ranging pixels each having photoelectric conversion units for receiving light fluxes that have respectively passed through first and second pupil regions, a reading unit shared by the 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 charge 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 after noise reduction, and the signal charge of the photoelectric conversion unit receiving flux with a higher transmittance is read first.