In this paper the real time operation of an automatic teller machine ((ATM)) is analyzed using a Timed Petri Net (TPN) model. In the modeling, the probability of arrivals, the speed and attentiveness of customers (clients) are taken to account. Different parameters are based on the statistical data. The model is simulated for 24 hours. The diagrams of number of succeeded customers, failed references to (ATM), idle times of (ATM) and wait times of customers are the outputs of TPN model.