A method for segmenting an image by a segmentation device using a CNN, comprising steps of: <a> performing <i> a process of acquiring a first segmented image for a t-th frame by allowing a CNN_PREVIOUS to segment the image of the t-th frame, wherein the CNN_PREVIOUS is a CNN having at least one first weight learned at a t-<i+1>-th frame, <ii> a process of acquiring at least some optical flow images, selected among each of optical flow images which corresponds to each of a <t-1>-th frame to a <t-i>-th frame, wherein each of the optical flow images corresponding to each of the <t-1>-th frame to the <t-i>-th frame includes information on optical flows originating with individual pixels of the first segmented image and ending with their corresponding pixels of each of segmented images of the <t-1>-th frame to the <t-i>-th frame, and <iii> a process of acquiring one or more warped images for the t-th frame by replacing first pixels with second pixels by referring to the optical flow images, wherein the first pixels include at least some pixels of the first segmented image for the t-th frame, and the second pixels include at least some pixels in at least some of the segmented images of the <t-1>-th frame to the <t-i>-th frame; and <b> performing <i> a process of acquiring loss values by respective comparisons between the first segmented image and the warped images, <ii> a process of acquiring a CNN_CURRENT, which is a CNN with at least one second weight having been obtained by adjusting the first weight of the CNN_PREVIOUS, by using at least one of the loss values, and <iii> a process of segmenting at least one image of at least one of <I> the t-th frame and <II> frames after the t-th frame by using the CNN_CURRENT. <a> performing <i> a process of acquiring a first segmented image for a t-th frame by allowing a CNN_PREVIOUS to segment the image of the t-th frame, wherein the CNN_PREVIOUS is a CNN having at least one first weight learned at a t-<i+1>-th frame, <ii> a process of acquiring at least some optical flow images, selected among each of optical flow images which corresponds to each of a <t-1>-th frame to a <t-i>-th frame, wherein each of the optical flow images corresponding to each of the <t-1>-th frame to the <t-i>-th frame includes information on optical flows originating with individual pixels of the first segmented image and ending with their corresponding pixels of each of segmented images of the <t-1>-th frame to the <t-i>-th frame, and <iii> a process of acquiring one or more warped images for the t-th frame by replacing first pixels with second pixels by referring to the optical flow images, wherein the first pixels include at least some pixels of the first segmented image for the t-th frame, and the second pixels include at least some pixels in at least some of the segmented images of the <t-1>-th frame to the <t-i>-th frame; and <b> performing <i> a process of acquiring loss values by respective comparisons between the first segmented image and the warped images, <ii> a process of acquiring a CNN_CURRENT, which is a CNN with at least one second weight having been obtained by adjusting the first weight of the CNN_PREVIOUS, by using at least one of the loss values, and <iii> a process of segmenting at least one image of at least one of <I> the t-th frame and <II> frames after the t-th frame by using the CNN_CURRENT.