Pure copper is widely used for various industrial products due to its high thermal conductivity, electrical conductivity, and friction properties. However, high-quality and high-efficiency connections of copper materials remain a challenge for industrial applications because pure copper has a low absorption rate of near-infrared light and is difficult to weld stably with a near-infrared laser. The light absorption rate for pure copper increases with shorter wavelengths. As such, visible light lasers should realize high-efficiency laser welding of pure copper. However, there are few reports comparing the laser wavelength dependence of welding efficiency for pure copper. In this study, bead-on-plate welding were performed on pure copper plates of 2 mm thickness using a 16 kW IR disk laser (1030 nm), a 3 kW green disk laser (515 nm), and a 1.5 kW blue diode laser (450 nm) to investigate the effect of laser wavelength on welding. Bead-on-plate welding of pure copper was performed in thermal conduction mode or keyhole mode by varying the laser spot diameter and power, and the amount of melting was measured from cross-sectional observations. As a result, compared to the IR laser, the blue and green lasers showed higher melting efficiency in both thermal conduction mode and keyhole mode, and the melting behavior was more stable.