An image pickup apparatus of the invention includes: an optical imaging system; an image pickup device; a defocus quantity calculation section for calculating a defocus quantity based on a phase difference between signals for focus detection obtained from pixels for focus detection; a high-frequency component quantity detection section for detecting a quantity of high-frequency component contained in a pixel signal outputted from a pixel other than the pixels for focus detection; a region determination section for determining in accordance with which of the defocus quantity and the high-frequency component quantity the optical imaging system is to be driven, according to a detection result of detecting in which of a plurality of divided blocks of the image pickup device an object of interest is present; and a focusing section for driving the optical imaging system in accordance with a determination result of the region determination section.