Abstract: An automatic focusing mechanism comprises a plurality of lenses and an image sensor disposed along an optical axis, an electromagnetic driving device for generating an electromagnetic force to drive the image sensor to move along the optical axis, and a position-limited device for limiting the movement of the image sensor along the optical axis. The image sensor is driven by the electromagnetic force and moved along the optical axis, and the distance between the lenses and the image sensor is properly adjusted, thereby realizing automatic focusing.