Abstract: The mat cutting apparatus includes a cutter for making a bevel cut and an adjustable edge guide having a vertical straight edge surface with which a vertical flat surface on the cutter is slidably engaged as the cutter is pushed along the edge guide to make a straight, beveled cut parallel to one edge of the mat. When used to cut an opening in a mat for mounting pictures or the like, the outline of the picture is traced on the back of the mat parallel to the edges thereof and then the mat is secured face down on the edge guide with the straight edge surface positioned adjacent and parallel to one traced line. The cut is made from the back surface of the mat such that the cut through the front mat surface registers with the traced line on the back mat surface. The mat is turned, the edge guide repositoined and the cutting process repeated until the mat opening is cut out completely.