[en] Thinning phenomena has been found in many nuclear carbon steel piping as the operation years increased. It is not possible to access to measure the piping thickness during power operation because of high radiation and high temperature. It needs remote monitoring equipment to monitor that piping thickness is above the design limit. KEPRI designed and developed on-line remote monitoring equipment using personal computer and ultrasonic wave. Here we introduce the principle of thickness measurement by ultrasonic wave and design and manufacturing of the equipment