[en] The interior of cell is crowded with various kinds of macromolecules, and proteins are designed to function under crowding environment. However, experimental studies showing the direct evidence of the effect of macromolecular crowding environment on the structures of proteins seems to be insufficient. Then, by the complementally use of both X-ray and neutron scattering methods, we have studied the effect of macromolecular crowding on both the structure and the hydration-shell of myoglobin. The neutral co-solute, polyvinylpyrrolidone (PVP, 40 k Dalton) was used to mimic the crowding environment of cell. The compression of the maximum dimension and the radius of gyration of myoglobin by the presence of PVP were observed. These changes are reasonably explained by the theoretical scattering function simulation based on the preferential exclusion model accompanying a collapse of hydration-shell of the protein. The present results suggest the possibility that the crowding environment by high molecular-weight neutral co-solutes would be non-ideal and different from small molecular crowding such as sugars and polyols.