1. A method for generating feature maps by using a device adopting CNN including feature up-sampling networks (FUN), wherein the device includes (i) a down-sampling block for reducing a size of an input image to thereby output a down-sampled input image; (ii) a plurality of filter blocks which include a (1-1)-th to a (1-k)-th filter blocks from which a (1-1)-th to a (1-k)-th feature maps are acquired by performing one or more convolution operations to the down-sampled input image; and (iii) a plurality of up-sampling blocks which include a (2-k)-th to a (2-1)-th up-sampling blocks each of which correspondingly interacts with each of the (1-1)-th to the (1-k)-th filter blocks, comprising steps of: (a) the device, if the input image is obtained, allowing the down-sampling block to acquire the down-sampled input image by applying a down-sampling operation to the input image, to thereby reduce the size of the input image; (b) the device, if the down-sampled input image is obtained, allowing each of the (1-1)-th to the (1-k)-th filter blocks among the plurality of filter blocks to sequentially acquire each of the (1-1)-th to the (1-k)-th feature maps by applying the one or more convolution operations to the down-sampled input image; and (c) the device (I) allowing the (2-1)-th up-sampling block among the plurality of up-sampling blocks to (i) receive the down-sampled input image from the down-sampling block, and (ii) receive the (2-2)-th feature map from the (2-2)-th up-sampling block, and then rescale a size of the (2-2)-th feature map to be identical to that of the down-sampled input image and (iii) apply a certain operation to the down-sampled input image and the (2-2)-th rescaled feature map, thereby acquiring the (2-1)-th feature map and (II) allowing, if M is an integer greater than or equal to one, the (2-(M+1))-th up-sampling block among the plurality of up-sampling blocks to (i) receive the (1-M)-th feature map from the (1-M)-th filter block, and (ii) receive the (2-(M+2))-th feature map from the (2-(M+2))-th up-sampling block, and then rescale a size of the (2-(M+2))-th feature map to be identical to that of the (1-M)-th feature map and (iii) apply a certain operation to the (1-M)-th feature map and the (2-(M+2))-th rescaled feature map in order to generate the (2-(M+1))-th feature map, thereby acquiring the (2-k)-th to the (2-2)-th feature maps, wherein the device, at the step of (b), applies a convolution operation to the down-sampled input image acquired from the down-sampling block via the (1-1)-th filter block among the plurality of filter blocks to obtain the (1-1)-th feature map, and then applies a convolution operation to the (1-M)-th feature map acquired from the (1-M)-th filter block via the (1-(M+1))-th filter block among the plurality of filter blocks to obtain the (1-(M+1))-th feature map, where M is an integer from 2 to (k−1).