An image processing apparatus according to an embodiment comprises processing circuitry configured to determine whether each pixel included in a radiation image is equivalent to point-like noise, calculate a degree of similarity between a first pixel and a second pixel that are included in the radiation image, conduct weighted averaging on the first pixel and the second pixel in accordance with the degree of similarity calculated, thereby performing a filtering process on the radiation image, and compare, if it is determined that the first pixel is equivalent to the point-like noise, first neighboring pixels located around the first pixel with second neighboring pixels located around the second pixel without using a comparison result between the first pixel and the second pixel, thereby calculating the degree of similarity.