A production facility of hot dip galvannealed steel plate dipping a steel plate in a plating bath, then alloying it, said production facility of hot dip galvannealed steel plate having a rapid heating furnace set above plating bath tank and adapted to have a heating capability of a 30°C/sec or higher heating rate and a 500°C or higher peak temperature and a soaking/cooling furnace set above said rapid heating furnace and treating the steel plate leaving said rapid heating furnace by at least one of soaking and cooling, said soaking/cooling furnace comprising a soaking region having soaking means adapted to soak the steel plate to 500°C to 650°C and a cooling region having cooling means adapted to cool the steel plate by a 5°C/sec or more average cooling rate, a ratio of lengths of the two regions (15, 16) in the furnace being freely settable, and a layout of said soaking region and cooling region being freely settable, wherein at least one pair of said soaking means arranged facing the two surfaces of the running steel plate in said soaking/cooling furnace and at least one pair of said cooling means arranged facing the two surfaces of the running steel plate are alternately arranged along the line direction of the steel plate, said cooling means sprays cooling medium from spray nozzles to the steel plate, and said spray nozzles are configured with ejection ports able to rotate about an axis parallel to a width direction of the steel plate, and wherein the ratio of lengths and the layout of the two regions (15, 16) are set in such a way that the soaking region is set by operating the soaking means continuing along the line direction from the entry side of the soaking/cooling furnace and setting them in the soaking state and by stopping all spray nozzles upstream of the soaking means set in the soaking state and setting them in the stopped state, and the cooling region is set by stopping all of the remaining soaking means to set them in the stopped state and by operating all of the remaining spray nozzles to set them in the spraying state. said production facility of hot dip galvannealed steel plate having a rapid heating furnace set above plating bath tank and adapted to have a heating capability of a 30°C/sec or higher heating rate and a 500°C or higher peak temperature and a soaking/cooling furnace set above said rapid heating furnace and treating the steel plate leaving said rapid heating furnace by at least one of soaking and cooling, said soaking/cooling furnace comprising a soaking region having soaking means adapted to soak the steel plate to 500°C to 650°C and a cooling region having cooling means adapted to cool the steel plate by a 5°C/sec or more average cooling rate, a ratio of lengths of the two regions (15, 16) in the furnace being freely settable, and a layout of said soaking region and cooling region being freely settable, wherein at least one pair of said soaking means arranged facing the two surfaces of the running steel plate in said soaking/cooling furnace and at least one pair of said cooling means arranged facing the two surfaces of the running steel plate are alternately arranged along the line direction of the steel plate, said cooling means sprays cooling medium from spray nozzles to the steel plate, and said spray nozzles are configured with ejection ports able to rotate about an axis parallel to a width direction of the steel plate, and wherein the ratio of lengths and the layout of the two regions (15, 16) are set in such a way that the soaking region is set by operating the soaking means continuing along the line direction from the entry side of the soaking/cooling furnace and setting them in the soaking state and by stopping all spray nozzles upstream of the soaking means set in the soaking state and setting them in the stopped state, and the cooling region is set by stopping all of the remaining soaking means to set them in the stopped state and by operating all of the remaining spray nozzles to set them in the spraying state.