PURPOSE: To switch step traverse by means of the simple constitution by turning a cam by utilizing the advance and retreat transfer of a drill spindle.

CONSTITUTION: A supporting member 6 which crosses at right angles to the axis line of a drill spindle 3 is fixedly installed onto the top edge part of a tile 5, and a rod 7 is rotatably supported onto the supporting member 6 with the axis line parallel to the spindle 3. A step cam 8 and a dog cam 10 are fixedly installed onto said rod 7. Therefore, the means for carrying-out the switching from rapid traverse to a drilling position to cutting traverse in several stages of step feed is constituted of the step cam 8 which advances and retreats, and revolves linked with the advance and retreat displacement of the tile 5, and the dog cam 10 which advances and retreats and revolves in the same phase to the step cam 8 and controls the hydraulic flow-rate adjusting valve 12 of a hydraulic cylinder apparatus 4.