PURPOSE: To prevent the accumulation of fine coal caused by such a phenomenon that the moistures contained in fine coal to be sampled and carrier gas are condensed in a L-shaped nozzle, by providing a heat insulating device to a sampling tube and providing a pressure gas supply pipe discharging and cleaning the fine coal accumulated in the sampling tube at a start time in the state connected to the sampling tube.

CONSTITUTION: A heat insulating apparatus is constituted so that an outer pipe 30 is provided to the part coming to the oscillating axis of a sampling tube 4 and heated gas is supplied to the annular passage 32 between two pipes. A porous air permeable filler 31 comprising glass wool is positioned at the end part of the outer pipe 30 or the lid 31a hermetically closing the end part of the outer pipe 30 is provided and a small hole 33 is further provided in the vicinity of the end part of the outer pipe 30 so as to heat and insulate the whole of the tube 4 by the supplied heated gas. Further, pressure gas is supplied to an ejector 35 through pipelines 36, 37. A branched pipeline 38 is provided to said pipelines and connected to the tube 4 through a valve 38a. By this method, because the pile of fine coal can be blown off prior to sampling, continuous accurate sampling work is enabled.