PURPOSE: To manufacture the perforated pipe having the slitted hole with the excellent out-of-roundness and preciseness of the inner diameter by forming the tape type material made, at least, its one edge end to the projecting/recessed shape to the spiral shape in closedly contacting or the pipe shape in vertically jointing, and welding the jointed seam of the edge end of the tape intermittedly.

CONSTITUTION: For manufacturing the perforated pipe, the recessed parts 2 of the length I2, the depth (d) at the intervals I1 are formed at one end edge of the tape type material being able to be welded (metallic tape, plastic tape, etc.). W shows the width of the tape type material. And this tape type material 1 is bent by the angle θ to the spiral type of closedly contacting, the opening part is made with the recessed part 2 at the jointed line of the edge end of the tape, the part except the recessed part 2 of the tape edge end, that is, the parts of the interval between the openings (the part of the length I1) are welded.