To reduce a work error at the time of connection of split parts along a peripheral direction in a pipe in which a projection ring is engaged with an outer surface of insertion opening of the pipe.

A projection ring 5 having peripheral split parts 6 is engaged with an outer surface of insertion opening 2 of a pipe 1. A pair of end portions 15A, 15B of the projection ring 5 at the split parts 6 is tightened by a tightening band 16 each other.