Provided herein may be an image sensing device and a method of operating the same. An image sensing device may include an image sensor obtaining an image using a plurality of pixels, and an image processor configured to use pixel values included in a region of interest included in the image to generate a gain table including gain table values corresponding to a first resolution, convert the gain table into a target table including target table values corresponding to a second resolution which is lower than the first resolution, and cancel noise included in the image based on the target table.