This paper presents the vibration control of a thin plate by multiple piezoelectric actuators and sensors which are co-located. To use piezoelectric materials efficiently, the Linear Quadratic Gaussian (LQG) controller is designed on the basis of a Multi-Input Multi-Output system so that each sensor monitors all the modes to be controlled and each actuator excites all the modes to be controlled. The robust LQG controller is then applied for attenuating vibration of a plate that is clamped along its edges and disturbed by a band-limited pseudo-random noise. This controller uses two sensor signal filters in order to control the first three natural modes of the plates. The results of the experiment show that the vibration of controlled modes are attenuated by 10 to 20 dB without destabilizing the other modes.