PROBLEM TO BE SOLVED: To use engineered components repeatedly obtained in plant design to the maximum and reduce an engineering design cost to the minimum. SOLUTION: The process plant design method comprises: (a) preparing a detailed design for a process plant in a production line including a detailed design of at least one engineered components; (b) preparing a detailed design for another process plant in a different product line wherein the detailed design of the at least one engineered components in (a) is reused in (b). COPYRIGHT: (C)2003,JPO