This paper describes a method of developing training system for cooperative Machine Maintenance Work (MMW) based on Networked Virtual Environment (NVE) technology. The development process consists of the two steps; 1. development of large-scale networked virtual environment based on a hierarchical server model which enables flexible and load balanced configuration of the whole system, and 2. application of ¡Çuser-centered design¡Ç to the design of user-interface for the collaborative work. A prototype training system has been constructed based on the proposed method, and the evaluation experiment has been conducted with users participation. It resulted in that the constructed prototype system could offer a sense of reality and co-presence of cooperative MMW training in NVE among users participated in the experiment.