This paper focuses on the experimental active flutter suppression of a cantilevered plate using piezoelectric actuation and modern control theory. Integrarion of a finite element method, a panel aerodynamic method, and the minimum state space realization yields the state space equation of motion for a fluttering plate. Distributed piezoelectric actuators are grouped into two equivalent actuators such that the controllability of the systems is maximized. A series of controllers are designed based on modern control framework, and the flutter suppression performance is evaluated via the wind tunnel testing. Among the designed controllers, u-synthesized controller shows the improved behavior over a wied flow speed range.