To realize a carbon-neutral society, it is necessary to shift from gasoline-powered vehicles to electric vehicles. Electric vehicles use copper components such as coil motors, batteries, and various wiring, for which copper joining technology is important. Additive manufacturing (AM) is one of the most essential technologies for the next generation of manufacturing. Therefore, the technology for forming pure copper layer on a pure copper substrate is important. Laser metal deposition (LMD) is one of additive manufacturing technologies. A blue diode laser is expected for effective in shaping pure copper parts because light absorptance of pure copper at blue light is higher than that of near-infrared light. Thus, a multi-beam LMD system with the blue diode laser in which metal powder was supplied perpendicular to the processing point and multiple lasers were irradiated from the surroundings was developed for additively manufactured pure copper. In our previous study, we succeeded in forming a pure copper layer on a pure copper substrate at a speed of 1.5 mm/s with blue diode lasers. However, an increase in processing speed was necessary for industrial application. It is considered that the improvement of energy density at the processing point and the control of heat input to the powder and substrate by lasers are essential to improve the processing speed. Therefore, in this study, we designed an optical system with 10 times higher energy density and calculated the heat input to the powder to form a pure copper layer at a speed of 10 mm/s or faster.