This research is investigating the efficiency level of a financial institution or banking in order to find out how a bank uses its resources optimally. A bank is considered efficient when it is capable of yielding output which is higher than the input. In this research, a case study on Bank Syariah Mandiri period 2013 – 2017 was carried out. By using the input and output variables, the optimality of the variables would be figured out. If one of the usage variables was not optimal, it would be inefficient. The efficiency level measurement was using Data Envelopment Analysis version 2.1 tool.