A vertical motion adjuster for a thermotherapy device includes a conveyance unit provided with a movable member configured to move along a mat, a support unit having a first side and a second side, the first side rotatably coupled to one side of the conveyance unit, and an elevation unit installed between the conveyance unit and the support unit and configured to adjust an angle of inclination of the support unit by raising or lowering the second side of the support unit such that the second side of the support unit is moved in the shape of an arc.