Non-destructive Inspection using ultrasonic waves is carried out and ultrasonic waves are sent to the welding area of the target by adjusting the position precisely using a servo motor. Ultrasonic waves can be used to measure and analyze the size and input time of signals returning through voltage, using data mapping techniques, since ultrasonic waves can strike the surface of objects outside of the first lane and the boundary of internal defects and then re-engage into the piezoelectric element(vibration) and generate voltages while vibrating again.