A new method for observing a nonlinear wave is proposed and illustrated with sample measurements. Observations are performed by using the time‐of‐flight method by counting the temporal upper hybrid wave packets which pass through the gap between two antennae. Two types of nonlinear waves were found in the experiment. One is outlined in the Korteweg de Vries equation by its behavior through the dispersion relation and the other behaves as a shock wave which represents the relaxing oscillation. The method of observation and the characteristics of the nonlinear waves are discussed circumstantially.