Structure of supercritical carbon dioxide at 320 K and at 9.2 MPa, 9.7 MPa and 10.2 MPa has been studied by neutron diffraction. For comparison, the gaseous state at 293 K and 1.0 MPa has also been studied. The intramolecular structure is practically independent of the state, that is, gaseous, liquid, solid or supercritical state. The structure factor shows a large increase in the small angle region (approximate to 0.3 Angstrom(-1)). This feature is in contrast to that previously found for the supercritical state far from the critical point by neutron diffraction by Bausenwein et al. (1992). The present diffraction result substantiates that the fluctuation of the densities is large in the region investigated