PURPOSE: To obtain a superconducting material having a high quality crystal only in a required direction by dividing one end of a high temperature heating zone into an upper and lower heating zone, inserting a pair of cantilever heating members into each of the upper and lower heating zone from left and right hand side, making the space between each of heating members variable and realizing three-dimensional temperature gradients.

CONSTITUTION: A low temperature heating zone A has an upper heating zone 2 and a lower heating zone 2a where same strengths of electrical power are each applied. A high temperature heating zone B is located on its right hand side. A high load density zone is divided in the longitudinal direction and each of the sections is provided with a bar-shaped heating member. The 3rd and the 5th heating member 6, 8 are each placed in each section of the upper heating zone and the 4th and 6th heating member 15, 17 are each placed in each section of the lower heating zone. The spaces between each heating section are made variable and each of the heating sections is independently controlled in terms of temperature. This heating system enables the homogeneous temperature distribution in the electrical furnace in X direction and the lowering of the temperature in the middle part than those of the edge parts, and realizes an ideal temperature distribution. Further, the 1st and the 2nd bar-shaped heating member generating heat of high load density 4, 12 are placed at the left end of the high temperature heating zone B and temperatures of these heating members are controlled independently from each other. The temperature gradients in Y and Z directions are produced by the move of the low temperature heating zone A on a rail 20 and the independent heating in vertical direction in the high temperature heating zone B, respectively.