Insert molding is used to manufacture products that combine metal and plastic. In this study, a special treatment was performed on the metal surface, and insert molding was performed to improve bonding strength between the metal and plastic. The metal surface treatment method involved nickel plating using inorganic particles. The type and size of particles and the height of plating were controlled. Artificial diamond and aluminum oxide were used as the particles, and the plating heights were 1/2, 1/3, and 1/4 of the particle size. Insert molding was performed with polycarbonate (PC) and PC containing glass fiber (GF), and a surface-treated metal sheet before plating. Then the adhesive strength of the metal and plastic specimens was measured. The adhesive strength varied according to the plating height and particle size, and the larger the particle size, the higher the bonding strength. The adhesive strength of the PC containing GF was 25% higher than the PC without GF. The metal surface treated by plating using aluminum oxide particles had better adhesive strength than the artificial diamond particles.