Recently, control PCB malfunction from failure frequently occurs in the arc welding machine in automobile and shipbuilding industry. However, there is no technical data on such a failure, it is difficult to analyze the root cause and prepare countermeasures. Furthermore, as the demand for high performance and high efficiency products increases, it is urgent to secure the reliability of the control PCB for arc welding machine. In this study, throughout the weak point detection test of quality and reliability for the arc welding machine control PCB, trouble shooting on the control PCB failure is prepared. To detect the weak point of the control PCB for temperature, humidity, vibration, thermal shock, and electrical stress, we perform the environmental test, the HALT, and the EMC test and improve the weak point detected from the arc welding machine.