Recently, the use of the wind turbine generator has rapidly spread as the one of the clean energy resources, and its size is becoming larger. Because of the difficulty of the maintenance of such a large wind turbine generator, the vibration analysis and clarification of the dynamical characteristics of the wind turbine generator are important. However, the conventional researches aimed at the fluid engineering in order to gain higher efficiency, and only several investigations have been reported in the area of the vibration analysis and its suppression. The wind turbine is a special type of rotating machinery: It has a long heavy blade which rotates in the vertical plane under the action of the gravitational force, and the wind power acting on the wind turbine blade varies periodically because the wind power increases as the function of the height. Therefore, it requires the original point of view in the dynamical analysis. This paper investigates the fundamental vibration characteristic of the wind turbine blade by using a rigid blade model. The gravitational force causes the effect of parametric excitation on the blade system. The interaction effect of the gravitational force and the wind force on the vibration of the turbine blade is investigated, and the occurrence of super-harmonic resonance is clarified. Also, the occurrences of the unstable vibration ranges are indicated. Furthermore, these results are validated experimentally.