PURPOSE: To execute excavation work safely without interfering with other equipment by a method wherein drainpipes for draining waste fluid or spring water from a facing in a shield pit in a small section to the rear side of a shield machine are extended in accordance with progress of excavation by the shield machine.

CONSTITUTION: In a method wherein a pipe 11 for drainpipe is fixed to a rear truck 5 of a shield machine and a drainpipe 13 is arranged to the rear side of the rear truck 5 and connected to the pipe 11 for the drainpipe and drainage is made from the facing through the pipe 11 for the drainpipe and the drainpipe 13 to the rear side of the shield machine, a suction hose 15 is interposed between the pipe 11 for the drainpipe and the drainpipe 13. The upstream end of the suction hose 15 is connected directly to the end of the pipe 11 for the drainpipe and the downstream side 15b of the suction hose 15 is connected with a connecting device to the upstream end 13A of the drainpipe 13. The distance between the pipe 11 for the drainpipe and the drainpipe 13 is adjusted by changing the position of the downstream side 15b connected to the upstream end 13A with the connecting device in the longitudinal direction of the suction hose 15.