To provide a useful objective protein coated with a protective protein, a protein complex that is produced in cells and has a structure that the objective protein is occluded with the viral occlusion body protein. A protein complex having the structure that the objective protein is occluded with the viral occlusion body protein, produced in insect cells or plant cells, preferably produced by incorporation of the objective protein in the crystalline form during crystallization of polyhedron derived from polyhedrosis virus, preferably a protein complex in which the polyhedrin contributes to improvement of stability, or protection, or improvement of preservability, or combination thereof, of the objective protein.