In a fusion splicing method and device for ribbon optical fibers, bare fibers (I) of the ribbon optical fibers are arranged, in opposite direction to each other, on a fiber setup stage (10) having V-grooves. A discharge occurs between the discharge electrode rods (21,22). In order to set all of the bare fibers “f” into a uniform temperature area in a discharge area, a wide and length of the uniform temperature area is extended by applying to the discharge area an electric field generated by applying a desired voltage to fiber clamps (31) made up of a conductive material. Thereby, a good fusing and splicing process is performed by supplying a uniform amount of heat to all of the bare fibers “f”. Further, the above process is also performed while a desired voltage is applied to a conductive plate arranged under the fiber setup stage (10).