1. An image device with image defocus function, comprising: an image capture unit capturing an image corresponding to an object; a depth map generation unit generating a depth map corresponding to the object; a processor coupled to the image capture unit and the depth map generation unit for determining an integration block corresponding to each pixel image of the image according to a practical depth of the depth map corresponding to the each pixel image and a variable depth corresponding to the each pixel image, utilizing the integration block to determine an integral image corresponding to the integration block, utilizing the integral image and an area corresponding to the integration block to generate a defocus color pixel value corresponding to the each pixel image, and outputting a defocus image corresponding to the image according to defocus color pixel values corresponding to all pixel images of the image; wherein the each pixel image of the image corresponds to a pixel of the image capture unit.