PURPOSE: To easily produce a radiator having special shape by inserting plural pieces of fins having the prescribed shape into sand mold so that the upper parts thereof are exposed, supporting, pouring molten base material into the exposed part and cooling to solidify the molten base material.

CONSTITUTION: The sand is filled while remaining a space 12 having the prescribed depth in a vessel-like casting box 10 at the upper part thereof, to constitute the sand mold 11, and plural pieces of fins 2 formed to the prescribed shape are buried into the sand mold 11 under almost vertical direction and fixed. Then, the upper ends of fins 2 are made so as to expose at about 10W15 mm from the sand mold 11. Next, the upper part of the casting box 10 is sealed by a cover 13 arranging a sprue 14 and the molten metal 3 heated at a little higher than the melting point of the fin material, is flowed in the space 12 from the sprue 14. Then, the exposed parts of the fins 2 are melted by heat of the molten metal 3, and by solidifying the molten metal 3, the base 4 having the same shape as the space 12 integrated with the fins 2 is formed. By this method, the radiator 1 having the fins 2 with the optional shape and size can be easily produced.