<p>An immunopotentiator containing immature DC as the active ingredient which is to be used in treating tumor after a thermal treatment, preferably a thermal treatment with the use of fine magnetic particles and still preferably a thermal treatment with the use of magnetite coated with a cationic liposome; a method of preparing an immunopotentiator containing immature DC as the active ingredient which is to be used in treating tumor after a thermal treatment, comprising culturing bone marrow cells taken out from a human subject with the use of a medium containing cytokines, preferably GM-CSF and IL-4; and a method of treating tumor which comprises carrying out a thermal treatment followed by an immunological treatment.</p>
