A reaction between deep-sea manganese nodule and(NH₄)₂SO₄ was carried out to find a new process for the extraction of manganese, cobalt, nickel and copper from deep-sea manganese nodule. Manganese nodule was decomposed with ammonium sulfate successfully and the effective components in manganese nodule such as manganese, cobalt, nickel and copper were extracted by water leaching of decomposed nodule. The optimum conditions of decomposition were as follows : the reaction temperature 500℃,(NH₄)₂SO₄ weight ratio manganese nodules 4.0, the reaction time 60min. The proper conditions of water leaching of decomposed nodule were as follows : the leaching temperature 100℃, the leaching time 2hr, amount of H₂O 200ml. Under above conditions, Manganese, copper, covalt and nickel in the nodule were extracted 99%, 99%, 93%, 90%, respectively.