PURPOSE: To bury an oval shaped pipe at a correct attitude by forming each sectional shape of a cutting edge pipe and a leading pipe to an inverted oval shape and excavating the circular part on the large diameter side by a main excavating head and by excavating the circular part on the small diameter side by a subexcavating head.

CONSTITUTION: A leading pipe 8 is connected at the top edge side of an oval shaped pipe 1, and a cutting edge pipe 9 is connected in oscillation-enabled form at the top edge of the pipe 8, and each sectional shape of the pipes 8 and 9 is formed to an inverted oval shape. Then, the soil and sand at the top edge ground is excavated by driving a main excavating head 13 installed at the top edge of a screw auger 10 inserted in the pipes 8 and 9 and a driving shaft 14 in the lower part in the cutting edge pipe 9. Then, the soil and sand in the large diameter side circular shaped part of the oval section which is excavated by the head 13 is discharged behind a screw blade 12, and the soil and sand in the small diameter side circular shaped part which is excavated by a head 15 is delivered to the blade 12, and discharged behind. Accordingly, the oval shaped pipe 1 can be easily inserted and buried.