This paper deals with the sensitivity analysis of efficient decision making units in Data Envelopment Analysis Method. First, the authors present a model which can be used when only single input variable is changing; then, a method suitable for the sensitivity analysis when several input variables are changing simultaneouslyis. Finally, the method is extended to the changes of output variables as well as the changes of output and input variables at the same time. The results are presented in the form of a numerical example.