Abstract: The present patent application discloses an envelope making plate. The envelope making plate includes a plate body with a marking groove, a reference edge; and a scale line or an indication line corresponding to the type of the envelope. The plate body is divided into a working area and a non-working area by the reference edge. The envelope paper abuts against or aligns with the reference edge. One side of the envelope paper is the working area, and another side is the non-working area. The marking groove is set in the working area of the plate body and intersects with the reference edge or an extension line of the reference edge. The marking groove divides the reference edge or the extension line of the reference edge into an acute angle and an obtuse angle. The scale line or the indication line corresponding to the type of the envelope is set along the reference edge and on the side where the marking groove and the reference edge form the acute angle.