To provide a small generator, capable of obtaining a sufficient electric power through generation by a powerful return force with a spirally wound spring and further serving as a crime prevention sensor, even though it has a small body because the generator is composed of a coil, a magnetic body, a spirally wound spring and a tire, and to provide a crime prevention sensor with the small generator and a crime prevention window.

The small generator consists of a coil, a rotation magnetic body, a spirally wound spring, and a rotating tire as its components.