front end with a guide groove cut like an acute angle and opening in the same direction as the opening and closing angle formed between the upper and lower blades 1a and 1b of the cutter 1 during cutting operation the cutter guide assembly a is so positioned that the lateral surface of the fabric selvage end guide 4 is contacted at a with a fabric selvage end 11 as shown which corresponds to a predictable minimum of fabric width when the fabric width changes during weaving so as to introduce a plurality of uncut weft threads 12a into the guide groove 5 as a result of this arrangement the distance between the fabric selvage end 11 and the cutter 1 is maintained substantially at the shortest constant distance and the fabric selvage end 11 travels in contact with the fabric selvage end guide 4 irrespective of a change in fabric width and will not be cut by the cutter 1 while the latter cuts the fringed selvage 12 to a minimum of length for uniform trimming to a constant length that is even if the fabric width decreases during weaving since the fabric selvage end guide 4 is positioned where it contacts the fabric selvage end 11 corresponding to a predictable minimum of fabric width the fabric selvage end 11 remains in contact with the fabric selvage end guide 4 so that there is.