An imaging apparatus includes a high-frequency pattern detector calculating a difference or a ratio between a value obtained by integrating averages of pixel outputs of a first pixel group arranged in identical positions in a vertical direction with respect to a focus detection pixel or in identical positions in a vertical direction with respect to another focus detection pixel located around the focus detection pixel and a value obtained by integrating averages of pixel outputs of a second pixel group arranged in positions shifted from the first pixel group in the horizontal or vertical direction, and sets a high-frequency degree in accordance with a magnitude of the difference or the ratio. An application determination unit increases the mixing rate of the focus detection pixel when the high-frequency pattern degree is high.