Repainting steel surfaces to prevent corrosion is one maintenance method for such large steel structures as old bridges. Unfortunately, the surface preparation process for repainting has workability and environment problems, despite using the highest-grade treatment blasting method. We propose a laser cleaning system using a fiber laser to solve these problems and describe our continuous-wave laser and a circle scan design as key technologies. System safety and standardization are briefly discussed. We introduce the maintenance problems of steel bridges in Japan to show the importance of the installation of our laser device.