An image processing device includes a camera unit, a control unit, an image processing unit and a storage unit. The camera unit obtains a first image. The control unit coupled to the camera unit adjusts an exposure value of the camera unit to control an average luminance value of the dark part of the first image and a contrast value of the first image. The storage unit is coupled to the control unit. The image processing unit is coupled to the camera unit and the storage unit, and it generates a second image according to the first image and a first algorithm stored in the storage unit, and generates a third image according to the first image and a second algorithm stored in the storage unit. The image processing unit generates a fourth image according to luminance values of the first image, the second image and the third image.