Abstract: An improved lumber positioning device on a carpentry cutting bench includes a rectangular board secured on the bench, a pair rip fences secured to the lateral edges of the board which has a number of oblique cutting grooves radically formed in center with pair of parallel transverse guide grooves beside the cutting grooves. The rip fences each has a number of corresponding oblique vertical slot communicating the cutting grooves, a pair of positioning plates slidably secured to a protrudent bar in the guide grooves each of which has a rack on an inner wall engageable with the serrated outer edge of a pair of expanding plates inside the positioning plates. A pair of positioning rods each has an elliptic eccentrically integrated at lower end engaged into the positioning plate for rotatably operated the expanding plates to lock or unlock the positioning plates to achieve a non-step gripping a cutting lumber on the rectangular board.