This paper proposes and develops a new non-contact active feedback control of leakage-flow-induced sheet flutter in a narrow passage, by injection and suction of fluid at inlet or outlet of the passage. The strategy of this active control technique is that the active feedback, which is by the activation of the injection/suction of the fluid at the inlet or outlet of the passage, suppresses the original source of the self-exciting fluid force acting on the structure, i.e., cancels the self-excited feedback mechanism. In this paper, the effective suppression of the leakage-flow-induced sheet flutter by the active feedback control technique is demonstrated experimentally. A flexible sheet, as a controlled object, is subjected to fluid flow in a narrow passage. The leakage-flow-induced flutter occurs to the flexible sheet in the translational motion over the critical flow velocity. The leakage-flow-induced sheet flutter is actively controlled and suppressed by the activation of injection/suction of the fluid at the inlet or outlet of the passage. The critical flow velocity under the controlled condition is examined with varying the controller gain and phase-shift between the injection/suction of the fluid and the sensor (vibration displacement) signal of the flexible sheet. As a result, it is indicated experimentally that the active feedback control technique increases the critical flow velocity, and suppress the leakage-flow-induced sheet flutter effectively. Moreover, the control performance is examined experimentally, and stabilization mechanism by the active feedback control is discussed.