In this paper, the authors propose a vibration control device using power generator in order to develop a small damper which is suitable for structural vibration control in space. The vibration control device consists of a ball screw, piston, ball nut, gear, power generator, and rod ends. The linear motion of the piston is converted into a rotary motion by the ball screw, and then the electric power is generated as dissipation of energy. A very low sinusoidal input displacement is applied to the device, and the characteristics of the damping force are examined with open circuit and short circuit of the generator. Experimental results are compared with theoretical results. Numerical simulation is applied to a flexible structure, by using sinusoidal input motion, and random motion.