A lens driving mechanism is provided for moving a lens unit along a light axis, including a frame, a base, a lens holder, and a driving assembly. The frame has plastic material and forms an opening. The base is in contact with and fixed to the frame, wherein a space is formed between the base and the frame. The lens holder is movably disposed in the space for holding the lens unit, wherein an external light enters the space through the opening to the lens unit. The driving assembly is disposed in the space and is connected to the lens holder and the frame, to impel the lens unit to move along the light axis.