PURPOSE: To cut and form a round prepared hole easily in the stage of cutting and forming a circular prepared hole on the surface of a pipe by rotating a top with which a cutting torch or guiding rollers are held in contact at all times one turn horizontally while tilting the same according to the surface shape of the pipe.

CONSTITUTION: In the stage of cutting and forming a circular prepared hole 12 on the surface of a pipe 11, a rotating and driving device 23 which can be rotated by a motor 22 is mounted to the projecting end 21A of a stanchion 21, and an arm part 24 mounted with a holder 42 having an air cylinder 53 and a top oscillating device 100 is disposed on the outer side of a fulcrum shaft 31. The holder 42 slides freely in the arc groove 41A of the device 100, by which a cutting torch 61 mounted to a top 41 and guiding rollers 47 thereof are pressed lightly to the surface of a pipe 11 at all times by means of the cylinder 53 and when the top is rotated one turn around the shaft 31, a round prepared hole is cut and formed easily in the pipe 11.