To provide a bonding technique for producing with high reliability a bonded part, which has less limitation such as application condition, excellent availability, less shape limitations, and is capable of continuous bonding, without hindering bonding reliability resulted from the formation of brittle intermetallic compounds at the bonding part, and excellent in corrosion resistance, etc., when bonding aluminum or an aluminum alloy and a steel material.

A copper alloy, a nickel alloy, or a silicon bronze base copper alloy are used as a wire 13 for MIG brazing. Aluminum 11 or an aluminum alloy and a steel material 12 are directly bonded by a MIG brazing method.