Abstract: In the disclosure, a plate-shaped fixing cover (30) is fixed to a lower part of a main shaft head (6). The fixing cover (30) protects a moving mechanism inside a column (5) from chips and the like. When the main shaft head (6) is positioned at an uppermost end of a movement range, a moving cover (40) covers and protects a portion of the column (5) that is exposed and not covered by the fixing cover (30). When the main shaft head (6) moves to the bottom end of the movement range, the moving cover (40) abut against the engagement projections (55A, 55B) and is restricted from moving downward. As the main shaft head (6) descends, the moving cover (40) moves upward relatively with respect to the fixing cover (30) and is housed on a back surface side of the fixing cover (30).