PURPOSE: To provide a general purpose drill screw for a very thick plate in which the projection of the drill part thereof on the rear side of a very thick plate can be eliminated, so that the danger of injuring the human body can be avoided, and also the manufacturing cost is low.

CONSTITUTION: Between a drill part 3 and a scerw part 2, a stem part 5 whose diameter is smaller than the diameter of the circumcircle of the drill part 3 is provided. A ring-shaped groove 6 for breakage use is provided to the part on the screw part 2 side of the stem part 5. After the drill screw for a very thick plate has been screwed in, impact is given to the drill part 3 projected on the rear side of a very thick plate 11 in the lateral direction. Then, the part of the ring-shaped groove 6 for breakage use is broken, and the stem part 5 and the drill part 3 is separately removed from the screw part 2.