PURPOSE: An automatic drilling machine, for use of water pipe, gas pipe, etc., with its handling made convenient by making a driving motor separable from the drilling machine main unit and providing a weight lightness.

CONSTITUTION: In the side of a drilling machine main unit 2, a motor 6 is removably installed to a mounting groove 9 of a movable unit 8, made up-down motion with a feed box 11, through a mounting plate 7. A rotary shaft 10 of the motor 6 is engaged to an input shaft 12 in the feed box 11, and rotation of the motor is transmitted to a drilling cutter 50. To a pipe b to be drilled, is mounted a drilling machine 1 through a saddle c, and the motor 6, if rotated, rotates the drilling cutter 50, and the feed box 11, being lowered by handling a feed handle 4, can make a drilling in the pipe b.