To provide a method in which mononuclear cells are differentiated into a good balance of NK cells, NKT cells, and T cells, and said cells are made to proliferate. The present invention provides a method for manufacturing an immune cell-containing composition, said method including the following steps: a first step in which mononuclear cells are cultured in a medium containing anti-CD16 monoclonal antibodies and either IL-2 and/or IL-15； and a second step, after the first step, in which culturing is performed under conditions that make the mononuclear cells preferentially differentiate into cytotoxic T cells. This method may also include a third step, after the second step, in which culturing is performed in a medium containing anti-CD16 monoclonal antibodies and either IL-2 and/or IL-15.
