Recently clean energy sources such as wind power and solar electric generation attract international attention. This paper presents anew clean energy source as one future alternative. In this system, electric energy is generated from the vibration energy of a flat plate which is placed in water flow. In particular a rectangular flat plate on which piezoelectric elements are glued is placed to rearward of a bluff body structure like a cylinder. The vibration energy of the flat plate induced by Karman vorteces is transformed into electric energy in the piezoelectric elements. Basic experiments are performed for this energy generation system.