Abstract: A PCB working machine includes a work table for holding a PCB substrate in place with a suction force; a spindle carrying a cutting tool; a controller for moving the spindle in accordance with a predetermined pattern; a collet chuck provided at a distal end of the spindle for clamping the cutting tool; a floating head encircling said collet chuck at a distant position and having an end plate in which a plurality of air blowing holes are provided; and an adjuster for adjusting the positional relationship between the floating head and the cutting tool.