An immunoadjuvant comprising one kind or two or more kinds of immunostimulating substances carried separately by two or more kinds of different microparticle immunostimulating substance carriers, and comprising at least a combination of (a) an inorganic substance such as microparticle calcium phosphate having a size phagocytizable by cells, and (b) precipitates of a soluble protein and a mucopolysaccharide formed by coacervation as the microparticle immunostimulating substance carriers, which is highly safe and can exhibit potent immunoadjuvant activity.