An upright posture assisting device for an X-ray inspection of infants, and more particularly to an upright posture assisting device for an X-ray inspection of infants, by which an infant can be X-ray photographed while being safely fixed. The upright posture assisting device for an X-ray inspection of infants includes: a body disposed on the front side of an X-ray detector and having an empty space in the interior thereof; an insertion hole formed on the upper surface of the body such that the legs of an infant are inserted into the insertion hole; and handgrip parts mounted on opposite sides of the upper surface of the body.