Abstract: A dedicated V-shaped groove forming machine comprises an X-axis slider disposed over a plate material so as be movable in an X-axis (groove forming direction); a Z-axis slider supported by the X-axis slider so as to be movable in a Z-axis direction (vertical direction); and plural cutting tools mounted on the Z-axis slider; and a Y-axis carriage for moving a plate material (workpiece) in a Y-axis direction (perpendicular to the X-axis direction). Further, there are provided work table adjusting device for adjusting the cutting tool movement locus in parallel to the work table and tool height detecting device for determining an origin in the Z-axis direction, etc.