The Ultrasonic welding has made possible to weld various ceramics to various metals at room temperature, quickly and easily compared to other welding methods. In addition, the weldability is improved by preheating. This paper shows to be possible to weld Al, Cu, Ag, and Mg (AZ31) in Si_3N_4 directly used ultrasonic vibration. Using the low melting metal, the weldability is better, welding strength is higher, and welding energy is lower. The welding energy used by ultrasonic welding is less than that used for resistance welding.