The present invention provides a method of adjusting light diffusing and light focusing capability of an optical element. First, an optical substrate having a first surface area is provided. Then, pluralities of pervious convexes are formed on an optical substrate, wherein the pervious convexes occupy a second surface area on the optical substrate. Diffusing effect of the optical element can be lowered/improved by increasing/decreasing an arrangement regularity of the pervious convexes. Diffusing effect enlarging/reducing the size of the optical element can also be lowered/increased by enlarging/reducing the size of pervious convexes. The focusing effects of the optical element can be improved/lowered by increasing/decreasing the ratio of the second surface area and the first surface area.