To provide a branching device for a synthetic resin pipe capable of easily constructing a branch part at a site even if there is no existing molding joint.

A branch hole 16 corresponding to the diameter of a body 12 of a branch member 11 is perforated in the circumferential wall of the synthetic resin pipe 2 and one end part 12a of the branch member 11 is fitted in the branch hole 16 so that a seal member 14 is interposed between the synthetic resin pipe 2 and a flange part 13. This device is also provided with a pushing member 15 pushing the flange part 13 of the branch member 11 toward the circumferential wall of the synthetic resin pipe 2.