A blue direct diode laser cladding system, which uses multi laser combining method, was developed in order to realize a high quality cladding layer having a dense, fine and purity. In order to clarify the mechanism of copper layer formation, the layer formation process when forming a copper layer using a blue direct diode laser was observed using in situ X ray observation. The six-blue diode lasers were guided to focusing head with every optical fiber, which core diameter is 100 μm. Beam profile at focal point of the combined six lasers was set a spot diameter of 400 μm. The focusing head has a function to supply a pure copper powder at a focal point from a center nozzle. As the results, it was found that the stainless steel 304 substrate was melted and generate some bubble in molten pool at laser fluence of 1221 kJ/cm2, and output power of 92W. At laser fluence of 407 kJ/cm2, the bubble was not appeared because only a slight molten pool was formed on the surface of the substrate. It was found that amount of bubble and penetration depth was depended on the laser fluence with blue direct diode laser. By controlling the amount of input energy, the copper coating was produced minutely with no weld penetration.