This paper proposes a new description method focusing on relations between businesses. This method is called Global Relations Diagram of function and demarcation (G-RD). In the computer application design, Current description methods utilizing ovals and allows like Data Flow Diagram (DFD) were widely used until now. However there are two problems with these description methods. Firstly, when this description method is utilized for a large-scale object, the arrow where it connects between the elements becomes entangled. Secondly, designed documents are not able to merge with other designed documents. G-RD can solve these two problems. It does this by describing the structure of the businesses by using “Elements” and “Relations”. Elements show the role and the function of the businesses, and Relations connect and explain the relationships between Elements. When Elements are plotted in the diagonal of square matrix, Relations are described at the intersections of the column and the row of two Elements. This paper introduces some case studies which were applied G-RD to design business processes, and to clarify the role and business assignment of each company after M&A. The effectiveness of G-RD has been evaluated at actual business field through over two hundreds of projects performed by Hitachi Ltd.