PURPOSE: To eliminate variance in treating time for a high melting point and to shorten the time by forming a solder layer thinly on one material to be joined and forming a higher melting point solder layer more heavily on the other material to be joined.

CONSTITUTION: A solder material is constituted of a thin first solder layer (Sn layer 5) which is formed by a vapor deposition or a sputter method on one material to be joined (semiconductor element 1) and a second solder layer (Pb layer 6) which is formed on the other material to be joined (die pad 2) and is provided with a higher melting point and a heavier thickness than the first solder layer. Then, both materials to be joined are superposed and heated to the temperature not more than the melting point of the first and the second solder layer to form an eutectic solder layer 7a; this two layered solder layer is heated to make a high melting point and both materials to be joined are soldered together. Thus, the treating time for a high melting point is extremely shortened.