To efficiently secure electric power by operating a pendulum body with the required minimum frequency of applying external force.

One end 3a of a coil spring 3 positioned corresponding to an upper face part 1c of the pendulum body 1 is fixed to an upper part lower face 2a in a case 2, and the other end 3b of the coil spring 3 is fixed to the upper face part 1c of the pendulum body 1. One side 1a of the pendulum body 1 is suspended under the influence of gravity from the upper part lower face 2a in the case 2 to put the coil spring 3 in a tensed state to apply energizing force in a direction to contract the coil spring 3. One end 4a of a coil spring 4 on the other side positioned corresponding to a lower face part 1d of the other side 1b of the pendulum body 1 is fixed to the lower face part 1d of the other side 1b of the pendulum body 1, and the other end 4b of the coil spring 4 on the other side is provided in a compressible/springing free state without being fixed to a lower part upper face 2b on the other side in the case 2. A compressed air injection port 7 is provided for accelerating upward and/or downward.