Since modernized production systems consist of automated equipments, any failure of equipments may cause serious problems on the shop floor. Especially in the electronics industry, the product life cycle is getting shorter and the reduction of product delivery time is becoming more crucial for a company to survive in the marketplace. This paper proposes a methodology for the efficient maintenance of industrial robots. In terms of the lubrication, we identified three maintenance factors of industrial robots; 1) the clefts of the decelerator; 2) excessive alien metallic substances on the U-axis, and 3) excessively long lubrication period. Based on the three factors, the proposed methodology is able to figure out the original reasons of failure as well as the solutions.