An ultraviolet screening agent comprising a plate-shaped silica composite manufactured by the manufacturing method of the present invention has excellent ultraviolet shielding properties by being dispersed in a plate form even though the agent is made of an ultraviolet screening material taking coal ash as a main reaction raw material. The method comprises the steps of: a) acid-treating the coal ash； b) manufacturing a plate-shaped silica composite； c) stripping the plate-shaped silica composite； and d) dispersing the silica composite in a liquid phase. 본 발명의 제조 방법으로 제조된 판상 실리카 복합체를 포함하는 자외선 차단제는 석탄재를 주반응원료로 자외선 차단 물질로 제조됨에도 판상의 형태로 분산된 형태를 취함으로써 자외선 차단 특성이 뛰어난 효과가 있다.
