In an image pickup apparatus capable of executing image pickup and focus detection using the phase difference scheme by a solid-state image pickup element, accurate and quick focus detection using the phase difference scheme is realized. In addition, an image pickup apparatus capable of obtaining a high-quality image signal even in an image pickup mode is provided. Each pixel unit of an image pickup element includes first and second photoelectric conversion units for photoelectrically converting light components that have passed through different regions in the exit pupil of an image pickup optical system and is arranged such that the first sensitivity distribution by the first photoelectric conversion unit and the second sensitivity distribution by the second photoelectric conversion unit overlap in a region between the photoelectric conversion units.