Abstract: A lens focusing device includes a lens holder, a winding fitted around the lens holder, and an outer case enclosing the lens holder therein. The outer case includes an outer wall portion, and multiple inner wall portions connected to the outer wall portion via multiple connecting portions. The inner wall portions are located between the lens holder and the winding, and respectively include an inner surface, an outer surface, and a first and a second side surface. The lens holder is formed on an outer face with confining areas, each of which includes a main surface and a first and a second raised side surface respectively facing against the inner surface and the first and second side surfaces, so that the inner wall portions are limited to move relative to the lens holder only within the confining areas. Therefore, the lens focusing device is impact-resistant and undue-twisting protected.