Weight reduction of vehicles has been undertaken to improve the fuel economy due to possible environmental impact of exhaust gas as well as out of concern over diminished fossil fuel. The weight of wire harnesses increases with the growing number of systems used in the vehicle. For the purpose of reducing the weight of wire harnesses, aluminum instead of the conventional copper is getting popular as a wire conductor. The conventional Al wire, however, is not able to be used for small gauge wires such as the sizes of 0.35mm2 and 0.5mm2 and wires used in the engine compartment due to its insufficient conductor strength. For this reason, we tried to develop a stronger aluminum alloy that has conductor strength equivalent to or stronger than that of copper. For the first time in the industry, we have successfully developed a high-strength aluminum alloy wire. Starting with the application to the 0.35mm2 wire for engine wire harnesses, we started its mass production in April 2015. This paper reports the development of high-strength aluminum alloy that can be used for small gauge wires and wires used in the engine compartment. The target property of aluminum alloy to be developed was specified as 220MPa tensile strength and 50%IACS conductivity. Based on the age-precipitated 6000 series aluminum alloy, additive elements and their content were specified and the alloy composition was determined. The aging conditions were determined by examining the precipitation status of Mg-Si intermetallic compounds. With this approach, we achieved 250MPa tensile strength and 52%IACS conductivity, both of which are better than the target. We have developed a 0.35mm2 wire that is 53% lighter than the same size copper wire.