1. An image processing method, adapted to an image processing apparatus, comprising: receiving an training image, which at least comprises a first pixel; calculating differences between the first pixel and a plurality of background candidates, wherein the background candidates are pixels respectively locating on other previously processed training images, and a coordinate of each background candidates is identical to a coordinate of the first pixel; finding a minimum difference among the differences; determining whether the minimum difference is larger than a first threshold; if no, generating a first output value according to the first pixel, the background candidates and a plurality of weightings corresponding to the background candidates; updating a first background candidate corresponding to the minimum difference by adding a first factor to the first background candidate, wherein the first factor is related to the first pixel, a first learning rate and the first background candidate; updating a first weighting related to the first background candidate by adding a second factor to the first weighting, wherein the second factor is related to the first output value, a second learning rate and the first weighting if yes, adding the first pixel as a new background candidate to the background candidates and adding a new weighting corresponding to the new background candidate to the weightings; and detecting whether a moving object existing in an incoming image according to the background candidates and the weightings.