An image fusion method and an image processing apparatus are provided. A first image is generated based on a first photographing parameter, and a second image is generated based on a second photographing parameter. A first pixel reference value of each of first pixels is calculated by using a self-define mask according to color components and a luminance component of the first pixels on the first image. A second pixel reference value of each of second pixels is calculated by using the self-define mask according to color components and a luminance component of the second pixels on the second image. A synthesizing reference map recording a plurality of synthesizing weights is obtained by comparing the first pixel reference value and the corresponding second pixel reference value. A fusion image is obtained by synthesizing the first image and the second image according to the synthesizing reference map.