In iterative software development methodology, a version control system is used in order to record and manage modification histories of products such as source codes and models described in diagrams. However, conventional version control systems cannot manage the models in a logical unit because the systems mainly handle with source codes. In this paper, we propose a technique of version control based in a logical unit for models described in diagrams. Then we illustrate the feasibility of our approach with the implementation of version control functions on a meta-CASE tool that is able to generate a modeling tool in order to deal with various diagrams.