PURPOSE: To make a manufacturing equipment small-sized, to reduce its installation space, and to reduce the cost of equipment, by bending like a snake motion a refrigerant pipe on which a flange is provided protrusively, cutting it at a prescribed pitch, bending it by a prescribed angle, and forming a fin.

CONSTITUTION: A linear refrigerant pipe 2 on which a flange is provided protrusively as one body is bent like a snake motion together with the flange 6. When a linear part 6a of the left end side is positioned so as to be inserted between forming dies 9, 10, and both the forming dies 9, 10 are brought close each other, the flange 6 is cut at a prescribed pitch by its edge parts 9a, 10a and is cut into many small pieces. Also, a fin 5 is formed by a movement of the approaching direction of both the forming dies 9, 10. In this way, the fin 5 is formed on the left end side in the flange 6 of the refrigerant pipe 2, and thereafter, the refrigerant pipe 2 is moved by 1 pitch in the left direction, and as to the second linear part 6a, the fin 5 is formed by the same process as mentioned above between both the forming dies 9, 10. By repeating said stage, the fin 5 is formed on all of the linear parts 6a of the flange 6, and a cooler with a fin is obtained.