An image processing apparatus includes a first synthesizing unit that determines a first synthesis ratio of a plurality of images based on correlation amounts between a reference image and the plurality of images excluding the reference image and synthesizes a first image from a plurality of images based on the first synthesis ratio, a noise reducing unit that reduces noise of a plurality of images including the first image using a plurality of parameters and generates a plurality of noise-reduced first images including at least an image obtained by reducing noise of the first image, and a second synthesizing unit that determines a second synthesis ratio according to the first synthesis ratio and synthesizes a second image from the plurality of noise-reduced images based on the second synthesis ratio.