The present study describes metal-metal bonding process using mixture of CuO nanoparticles and Ag2O nanoparticles (Ag2O/CuO mixed particles). The leaf-like aggregates with a longitudinal size of 1116 nm and a lateral size of 460 nm composed of CuO nanoparticles with a size of ca. 10 nm and the Ag2O nanoparticles with a size of 20.6 nm were fabricated with a salt-base reaction. Metal-metal bonding could be successfully performed by using the mixed particles as a filler sandwiched between metallic discs and pressurizing the discs at 1.2 MPa for 5 min under annealing in H2 gas at 400oC. The mixed particles bonded not only metallic Cu discs but also metallic Ag discs strongly; The shear strengths were as large as 17.3 and 22.4 MPa for the Cu discs and the Ag discs, respectively.