Due to the rapid changes in the business environment, the shortening of product and service life cycles, and the necessity of technology integration at all levels of industry, the need for process orientation in organizations is clearly evident. Therefore, designing an organizational structure based on processes emerges as a fundamental necessity. This research aims to provide a comprehensive methodology for developing an optimal organizational structure, with a focus on Bank Melli Iran as a case study. Initially, the strategic components of the bank were analyzed, and then a list of Bank Melli’s processes was developed based on the American Productivity and Quality Center (APQC) standard. Following this, through interviews with bank experts, the existing processes were identified and analyzed. Additionally, a process architecture document was created, and the bank's legal and regulatory constraints were also examined. Finally, by aligning the identified processes with the results obtained from previous stages, an optimal organizational structure for Bank Melli Iran was proposed, which can lead to improvements in organizational efficiency and flexibility.