To fix mounting parts surely, and to attain sufficient joint strength in a reflow soldering method.

The circuit board, in which conductor patterns 3a, 3b are drawn on a surface and a cured thermoplastic adhesive layer 2 is exposed 2a in a surface section on which the conductor patterns 3a do not exist, is formed. The circuit part 4 is placed at a mounting prearranged place on the circuit board so that the electrode sections 4a, 4b of the circuit board are brought into contact with corresponding terminal patterns on the conductor patterns 3a, 3b. The circuit part 4 is bonded and fixed onto the circuit board by heating the thermoplastic adhesive layer 2, melting the layer 2 again, cooling it and curing it again.