1. A method of enhancing resolution of video, comprising: reducing at least one training video having a high-frequency component by a specified reduction ratio in at least one direction of a vertical direction and a horizontal direction to generate a reduced video having at least one first spatio-temporal box; extracting the high-frequency component from the training video to generate a high-frequency component video having at least one second spatio-temporal box; calculating at least one first feature vector including a feature amount of the first spatio-temporal box of the reduced video; storing, in a look-up table, a plurality of pairs each having the first feature vector and the second spatio-temporal box at a position equivalent to that of the first spatio-temporal box; magnifying an input video including a third spatio-temporal box by an magnification ratio of an inverse number of the reduction ratio in at least one direction of the vertical direction and the horizontal direction to generate a temporary magnified video having a fourth spatio-temporal box; retrieving, a first feature vector similar to a second feature vector including a feature amount of the third spatio-temporal box of the input video, as an element, from the look-up table; and adding the second spatio-temporal box stored in the look-up table, corresponding to the retrieved first feature vector, to the fourth spatio-temporal box at the same position as that of the third spatio-temporal box to generate an resolution-enhanced video.