A height-adjustable splint, according to one embodiment of the present invention, comprises: a support plate (1000), mounted on teeth of the lower jaw, in a structure capable of being filled with a thermoformable resin； a front teeth portion relation recording apparatus (6010) for fixing a gap between front teeth of the upper jaw and front teeth of the lower jaw, on which the support plate (1000) is mounted, at the upper portion of a front teeth part of the support plate (1000) where the front teeth of the lower jaw are positioned； and an auxiliary support plate (2000) mounted on the upper portion of a molar portion of the support plate (1000), positioned on a molar tooth of the lower jaw, in a structure capable of being filled with a thermoformable resin, wherein the auxiliary support plate (2000) is characterized in that the height where the auxiliary support table (2000) is mounted on the support plate (1000) is determined in accordance with the pressure applied to a molar tooth of the lower jaw and a molar tooth of the upper jaw, on the basis of positions of the upper jaw and the lower jaw presented by the front teeth portion relation recording apparatus (6010).
