Energy harvesting systems convert ambient energy from environment such as vibration, sunlight, wind, temperature gradient, etc. into electrical energy. Among several ambient energy sources, wind energy can be considered as one of the most promising sources because of its attractive features such as efficiency and economic merit. However, if an ordinary type of wind turbine is used for providing the electricity to low-power equipments (e.g., light poles, wireless sensors for structural health monitoring, etc.), it might be too inefficient and too costly. Recently, on the other hand, alternative (or innovative) approaches for wind power systems have been investigated by focusing on the aerodynamic instability phenomena such as galloping, flutter and vortex shedding. This paper first proposes a new energy harvesting system using wake galloping. To this end, the energy harvesting system based on wake galloping is designed and manufactured. And then, a series of wind tunnel tests are carried out in order to validate the efficiency and effectiveness of the proposed energy harvesting device. From these tests, the applicability of the proposed energy harvesting system using aerodynamic instability (i.e., wake galloping) is experimentally verified. Therefore, it can be an efficient energy harvesting system. Moreover, it can be used as an alternative energy source for low-power equipment, resulting in much simpler structural health monitoring systems without batteries for wireless sensors.