PURPOSE: To improve the cooling in the peripheral part of a furnace with cooling pipe lines of simple structure and to achieve the resistant of cooling at the center part of the furnace.

CONSTITUTION: In the structure of the furnace bottom part of the blast furnace provided with plural cooling pipe lines 10 embedded parallel in refractory 3 having high heat conductivity under the bottom plate 3 at the furnace bottom so as to cross the whole width of the furnace bottom surface in the unidirection, besides the existing cooling pipe lines 10, plural pieces of additional cooling pipe lines 11 crossing the furnace center line forming the boundary line (a) in the same direction are added. IN the peripheral part of the furnace, the additional cooling pipe lines 11 are positioned at the lower level than the existing cooling pipe lines 10 and embedded into the refractory 2' having low heat conductivity, and in the center part of the furnace, this additional cooling pipe lines are positioned to the same level as the existing cooling pipe lines 10, and on the other hand, the existing cooling pipe lines 10 in the center part of the furnace are positioned by changing their positions downward, and cooing performance in the peripheral part of the furnace and in the center part of the furnace are independently controlled.