PURPOSE: A composition for anti-cancer containing seaweed extract is provided to ensure indication of blood cancer, colon cancer, skin cancer or lung cancer and to apply to a pharmaceutical composition or food composition. CONSTITUTION: A composition for treating blood caner contains seaweed extract or fraction thereof as an active ingredient. The seaweed is Petalonia binghamiae, Sargassum nipponicum Yendo, Dictyopteris divaricata or Myelophycus simplex. The extract isolated using methanol, distilled water, ethanol, acetone, ethyl acetate, saturated normal butanol, chloroform, methylene chloride, water or mixture thereof. The seaweed fraction is obtained by removing extraction solvent from the seaweed extract to obtain solid extract, and fractioning into ethanol layer and ethylacetate layer.본 발명은 항암제 조성물에 관한 것으로, 구체적으로는 미역쇠(Petalonia binghamiae), 꼬마모자반(Sargassum nipponicum Yendo), 미끈뼈대그물말(Dictyopteris divaricata), 바위수염(Myelophycus simplex) 등의 해조류 추출물을 유효성분으로 하는 항암제 조성물에 관한 것이다.