This study examined, as the one way of using zeolite, the effect about the removal of ammonia nitrogen and phosphorus that cause the eutrophication occurred the adjoining seas. 4A type zeolite was used as an adsorbent to remove NH₄-N, PO₄^3--P ion in the artificial seawater. Zeolite is more required than in the fresh water, under the same conditions, in order to remove NH₄-N in the sea water. The lower the thickness of NH₄-N is in the early stage, the more Freundlich type equation the value of 1/n increases. In case of PO₄^3--P indicated that the removal efficiency was relatively independent of PO₄^3--P concentration. Freundlich parameter 1/n has the value under 2. So it shows that absorption is made with relatively ease.