Image processing apparatus, image capturing apparatus, image processing method and storage medium

There is provided an image processing apparatus comprising: an acquisition unit configured to acquire captured images captured by a plurality of image capturing units for capturing an object from different viewpoints; a specifying unit configured to specify a defective image from the plurality of captured images; a determination unit configured to determine a weight for each captured image based on a position of the image capturing unit that has captured the defective image specified by the specifying unit; and a synthesis unit configured to generate a synthesized image by weighting and synthesizing the plurality of captured images based on the weights determined by the determination unit.