An active stylus includes a tube, a signal emitting module, a power module, an electrical energy storage device, a movable element and an energy transformation module. The signal emitting module, the power module, the electrical energy storage device and the energy transformation module are disposed in the tube. The power module is electrically coupled to the signal emitting module, and the electrical energy storage device and the energy transformation module are electrically coupled to the power module. The movable element is movable in the tube. The energy transformation module is configured for transforming energy generated by motion of the movable element into electrical energy. The electrical energy transformed by the energy transformation module is stored in the electrical energy storage device by the power module.