An image processing apparatus capable of correcting an error during computation of a correlation degree without storing data for correcting distance information in advance in a recording medium, to highly accurately form a distance image. The image processing apparatus has a distance estimation unit that estimates a subject distance in each area, from a correlation degree of a plurality of images, a distance reliability calculation unit that calculates the reliability of the subject distance estimated by the distance estimation unit, and a distance image forming unit that corrects the subject distance estimated by the distance estimation unit based on the reliability calculated by the distance reliability calculation unit and to form a distance image based on the corrected subject distance.