To understand the functioning of any organization it is necessary to understand the functional structure of that organization. A bank is a commercial organization. The bank has to take some decisions. Plans have to be made. They have to be implemented. How is decision making done in a bank? How those decisions are implemented. In order to understand this, an attempt has been made in this article to know how the functioning of large size banks is structured in general. For that, the decision process of the bank and the process of implementation of the decisions have been studied in this article.