To provide a heat insulation member for a high-temperature furnace which can realize in an improvement in productivity due to reductions in a purchasing cost of a carbon felt, man-hours of replacing and repairing and a repair stopping time by reducing a replacing frequency of another furnace constituting component by prolonging a lifetime by suppressing waste of the carbon felt for a CO2 gas generated from a work.

The heat insulation member 10 comprises a carbon sleeve 4 installed on an inner surface of the carbon felt and having a bulk density of 1.6 to 1.8 g/cc in the high-temperature furnace having an inner cylinder disposed on a periphery of the work to be inserted to form a furnace inner space, an outer cylinder for constituting a shell of the furnace, and the heat insulation member 10 having the cylindrical carbon felt inserted between the outer and inner cylinders.