To improve sweeping effect by providing a lance tube and a nozzle capable of sweeping any surface arranged at a place in a long distance from the nozzle.

Nozzles 56, 58, arranged in a pair of axial directions, are incorporated into a nozzle assembly 54. The nozzle assembly 54 is connected directly to lance tubes 14 and is provided with inlet ports 60 for being extended into the lance tubes 14, and outlet ports 62 exposed to the outside of the lance tubes. According to this method, sweeping medium, supplied to the lance tubes 14, flows into the inlet ports 60 of nozzles, then, passes through the throat units 64 of the nozzles and, thereafter, is discharged out of the outlet ports 62. The throat surface 64 is specified by symmetrical rotating surfaces about the center line 72 of the nozzle and is constituted of a curved line consisting of segments rotated about the center line 72. In this case, the rotating surface is provided with a tapered part 70 neighbored to the inlet port 60, and a truncated part 68 connected to the tapered part 70 and extended to the outlet port 62 while forming a neck part, arranged between the inlet port 60 and the outlet port 62 so as to have a part having the minimum diameter.