PURPOSE: To improve the efficiency of coupling work, to reduce production cost and to improve productivity by carrying out mechanical coupling of a parallel pipe to a coupling band and by joining the coupling band to the parallel pipe through tight fitting so as to form a firm coupling pair in the plane shape.

CONSTITUTION: An engagement recess part to be engaged with an outer peripheral part of a parallel pipe 3 is elastically provided on a coupling band 5, a pressurizing device 8 for press-fitting each window of the coupling band 5 one by one from one side part to the other side part is arranged on the parallel pipe 3, and the pressurizing device 8 is operated by hydraulic or pneumatic pressure. And the operation is intermittently executed with a predetermined time difference by an electric control device 14. By fitting the coupling band to the parallel pipe by the pressurizing device, the efficiency of coupling work is improved and a stable production is enabled. Also, the production cost is reduced and the productivity is improved.