For the survival and growth, every organization should be capable to translate its mission, vision, goals, objectives, plans and programs enhancing performance. Rastriya Banijya Bank limited (RBBL) was incorporated in 1966 through enactment of special statute on Rastriya Banijya Bank (RBBL) Act.1966, with mains objective to provide banking and financial service related business in the country. In this context, this article explores the capacity and performance level of Rastriya Banijya Bank limited and discussion about contribution of RBBL in banking business in Nepal. Continuous performance is the objective of any organization because only through performance, organizations are able to grow and progress. For the discussion, about Performance of RBBL, operating status of RBBL, financial status of RBBL, total investment Share and loan investment, dividend received, contribution on business credit transfer, Revenue generation, Shareholder's Fund/net-worth, working capital, administrative and unfunded liabilities of RBBL on the based on PBM theory assumptions. Secondary data are obtain from Ministry of Finances and National planning commission and some of the key personnel of the RBBL are also interviewed. The finding shows that there are still very important roles of RBBL for service delivery system, social and economic development, and the roles of income Tax; value added tax and not taxable-tax collection and social welfare, Employees' generation, curtailing, syndicate and market control, the role of crisis management and emergency situation etc.