1. An image processing apparatus capable of generating a combined image by combining a plurality of images, the apparatus comprising: an acquisition unit configured to acquire a plurality of images including a first image having a first exposure, a second image having a second exposure that is higher than the first exposure, and at least one low-noise image having a higher signal-to-noise ratio than the first image; a moving region detection unit configured to detect moving regions in which a difference between the first image and the second image is greater than a predetermined value; a brightness calculation unit configured to calculate a brightness of the moving regions; a replacement region setting unit configured to set replacement regions from among the moving regions based on the brightness detected by the brightness detection unit; and a combining unit configured to combine the plurality of images, wherein the combining unit is configured to generate a combined image by combining the first image and the second image, and replace the replacement regions in the combined image with an image of a region corresponding to the low-noise image.