An image processing method for a fluorescence reaction region of teeth. The image processing method includes emitting blue light from a light source to illuminate the teeth in a mouth, so that the teeth generate fluorescence； capturing a first teeth image of the teeth by an image capturing unit； separating the first teeth image into a first red-value image, a first green-value image, and a first blue-value image by a processing unit； transforming the first red-value image into a second red-value image by the processing unit using a pixel value transforming function； and combining the second red-value image, the first green-value image, and the first blue-value image into a second teeth image by the processing unit.
