An image processing apparatus includes a setting unit, a small region setting unit, a determination unit, a search unit, a noise reduction unit, and a synthesis unit. The setting unit sets a target patch in an input image. The small region setting unit sets a small region near the target patch. The determination unit determines a number of similar patches to be detected as a patch similar to the target patch based on a noise amount in the small region. The search unit searches the input image for the similar patch based on the number of similar patches. The noise reduction unit configured to perform noise reduction processing with respect to the target patch using the target patch and the similar patch. The synthesis unit generates an image by synthesizing a plurality of patch groups subjected to the noise reduction processing.