PURPOSE: To change the film-thickness of each of two circuits so as to improve the heat resistance of a fusible substrate by forming only one fusing circuit on a heat- resistant substrate, and then monolithically connecting and fixing the fusing circuit to the electrode of the power supply circuit formed on an insulating substrate.

CONSTITUTION: A fuse board is provided with a fusing member 12 prepared through the process of forming only fusing circuit 21, made of a fusing material, such as copper, tin, lead, a solder alloy or the like, on a heat-resistant substrate 20 made of alumina ceramics or the like. Meanwhile, the fuse board is provided with also a circuit substrate 11 prepared through the process of forming a power supply circuit on an insulating resinous-substrate 13 made of glass epoxy-resin, polyimide or the like. Then both ends of the circuit 21, whereto solder plating 22 is already given, are laid on top of the electrode 15 of the circuit substrate 11, printed with soldering paste 17, to be subsequently heated so that their solder may be heat-welded together to be monolithically fixed. Since the circuit 21 and the electrode 15 are formed separately from each other, the film-thickness of each of them can be optionally controlled so as to provide improvement in the fusing accuracy of the fuse board and a reduction in the resistance of the power supply circuit.