We describe here the research work concerning the development of the CAPP(computer aided process planning) system, named BLOCK. designed to support block division of ship. The system consists of the expert system part generating block division lines, and their evaluation and editing one. As a reasoning approach of expert system, the case-based reasoning is used. The division lines can be graphically edited and the satisfaction measure of block division can be checked up in the evaluation stage with separate window. The expert system is developed by using NEXPERT Object development tool in the workstation. Currently the target ship is VLCC.