To simplify the structure and reduce the cost by arranging a connecting hardware to be connected to the upper end of a riser pipe on the lower end of a flexible strap body, arranging a suspending support metal fitting capable of being engaged with a hull side receiving tool on the upper end of the strap body, and specifying the length of the strap body.

A flexible strap body 3 is arranged to suspend a riser pipe 1 from the rotary table 9 of a working deck 5. At this time, the length of the linear body 3 is set in such a manner that the top part of the riser pipe 1 is lower than a hull moon pool 2 when the riser pipe 1 is suspended from the table 9 as receiving tool. A flange 4 with eye as a connecting hardware to be connected to the riser pipe 1 is set on the lower end of the linear body 3. Further, a support hardware 7 with eye as a suspending support hardware capable of being engaged with the table 9 is arranged on the upper end of the strap body 3. The support hardware 7 is put on the upper surface of the table 9 to support the downward vertical force of the riser pipe 1. Thus, the hang-off operation is easily performed, and a flexible joint or hydraulic mechanism can be dispensed with to reduce the cost.