Abstract: Apparatus for making corner joints of sealing plastic profiles, or moldings, for windows, doors or the like, including a base plate on which two profile holding means, each having a bottom formed with a groove for accommodating the continuous profile to be held and a pivotable lid for covering or opening the accommodating groove are mounted, one fixedly and one pivotally. A welding means pivotable relative to the holding means, is provided which cuts the miter with the holding means in line and heats the cut edges. The pivotal holding means is moved toward the fixed one and the cut and heated edges of the profile are welded together.