To prevent coming-off of joint material by disposing a predetermined shaped reinforcing bar in a ring-configured interstice defined between the side surface hole of a manhole and an attachment pipe.

A constant width flat surface 1a is formed on one surface of a spirally wound synthetic resin wire material, and a reinforcing bar 1 is formed by heat welding the flat surface 1a on a pliable synthetic resin bottom plate 2 with generally the same width. Next, on the pipe end outer peripheral surface of an attachment pipe 4 inserted in the side surface hole 3a of a manhole 3 from its outside, a bottom plate 2 is wound by the use of a double pressure sensitive tape 5, and then the reinforcing bar 1 is disposed in a ring-configured interstice 6 between the side surface hole 3a and the attachment pipe 4. Following this, joint material 7a consisting of resin-blended cement mortar is charged in the interstice 6 for forming an inner joint 7a for clogging the interstice 6. Thus, entanglement holding of the joint material can be done and the reinforcing bar can be fitted easily.