PURPOSE: To provide a graphite block heating device which can heat a graphite block in a narrow, long form uniformly to a high temperature in a narrow, long space of a hexagonal column and which can also heat this narrow, long graphite block to a high temperature while maintaining the adjoining border part with it at a low temperature.

CONSTITUTION: The graphite block heating device is provided with a hollow cylindrical heater 2 enclosing the outer periphery of a narrow, long cylindrical graphite block 1, a heat insulating material 4 enclosing the outer periphery of the heater and the faces of both ends of the graphite block in the axial direction and a hollow cylindrical vacuum container 6 enclosing the heat insulating material. The outer surface of the heat insulating material is spaced slightly from the inner surface of the vacuum container and the graphite block and the heat insulating material have center holes 1a and 4a formed passing in the axial directions and a plurality of air holes formed passing from the center holes in the radial directions.