The aim of this study was to develop a quality management system for in-service training for vocational training instructors for increasing training effectiveness in the long term. To achieve this purpose, focus group interviews were conducted for practitioners and instructors of vocational training to analyze the current status and problems of in-service training. Based on the ADDIE model, the interactive model, and the PDCA model for developing vocational training programs, the quality management system was developed for in-service training for vocational training instructors. Then, the developed quality management system was reviewed from the experts to establish the validity. Finally, nine stages including 61 sub-steps to be performed in each stage were developed according to the PDCA process. Additionally, the use of learning management system was presented at each stage in the quality management system.