As fuel-related regulations are being strengthened, the government is working to improve fuel efficiency and reduce exhaust emissions. Efforts are being made to solve the problem by increasing the engine efficiency or reducing the weight of the vehicle. However, improvement of powertrain such as engine is difficult to achieve fuel efficiency and exhaust gas regulation, and weight of vehicle has been greatly increased due to convenience of users and safety devices. However, upgrading function of powertrain such as engine is difficult to achieve fuel efficiency and exhaust gas regulation. Consequently, weight of vehicle has been greatly increased due to convenience of users and safety devices. In order to solve the problem, the method reducing the weight of the vehicle has been changed from a conventional steel to a lightweight material or non-ferrous metal welding method. Therefore, It is required for new potential welding and mechanical bonding methods. Friction Stir Spot Welding is one of Friction Stir Welding. It is similar to resistance spot welding and does not involve melting due to the solid-state welding method using the rotational force and pressure of the tool. Self-Piercing Riveting (SPR) is a mechanical bonding method using rivets. Unlike conventional rivets, drilling or alignment process between the material and the rivet machine are not required. Therefore, this study intended to perform lap welding of 3mm thick aluminum alloy (A356) and 2mm thick automotive steel sheet (SAPH440) in terms of FSSW and SPR methods. Bonding characteristics were investigated according to the variation of plunge depth and rotational speed (RPM) of friction stir welding, and the bonding characteristics according to the depth and diameter of the SPR lower mold die were observed. Through this study, the highest shear - tensile strength of friction stir welding spot was obtained at the depth of 1.0mm, depth of rotation of 500RPM, SPR of rivet length of 7mm, die depth of 1.2mm and die diameter of 10mm.