A swinging apparatus comprising an energy provider and a swinging mechanism disposed thereon. By means of adjusting the size and shape of the swinging mechanism and adjusting a distance between the swinging mechanism and the energy provider so as to control the ratio of the distance between the swinging mechanism and the energy provider to a characteristic value corresponding to the swing mechanism in a range between 4 and 0.25, the swinging frequency of the swinging mechanism may be adjusted automatically to comply with the variation of the motion frequency of the energy provider. The present invention further provides an energy harvester to work with the swinging apparatus and a coil to generate an induced current for power generation during the swing of the swing mechanism. In the present invention, the natural frequency of the swing mechanism may be adjusted according to the rotational velocity of the energy provider.