To provide a boring device capable of carrying out boring work even if there is not sufficient space for the boring work at a lateral side of a pipe when boring a gas pipe through a branch joint attached to the gas pipe by laterally placing a vertical flank connected with a branched pipe.

A plunger 17 of a hydraulic cylinder 18 is fixed to a rod 23, and a hole saw 21 is fixed to a cylinder 16. When boring the gas pipe 1, the rod 23 is operated, and the hydraulic cylinder 18 is installed into a hole saw charging port 14 and pressed to the vertical body 13 together with the hole saw 21. After positioning, oil is fed to the hydraulic cylinder 18, the hole saw 21 is advanced and pressed to the gas pipe 1 together with the cylinder 16, and bores the pipe.