1. An object pose normalization method comprising: determining, performed by at least one processor, a pose of a non-frontal image of an object by determining a center line dividing object feature points of the non-frontal image and using a symmetrical relationship obtained by mean distances between the object feature points and the center line; performing smoothing transformation on the non-frontal image of the object, thereby generating a smoothed object image; and synthesizing a frontal image of the object by using the pose determination result and the smoothed object image, wherein, in the determining of the pose a first mean distance, of the mean distances, is obtained between a first plurality of object feature points existing in one side of the center line of the non-frontal image and the center line, and a second mean distance, of the mean distances, is obtained between a second plurality of object feature points existing in another side of the center line, different from the one side, of the non-frontal image and the center line, and the first mean distance is compared with the second mean distance to determine the pose.