The effect of pressure on the Raman active inter- and intramolecular vibrations of the hexachlorobenzene crystal was studied under hydrostatic pressure up to 5.5 GPa. The Raman frequencies of the inter- and intramolecular vibrations increased monotonically and some bands due to the degenerate intramolecular vibrations were resolved into doublets with increasing pressure. The pressure-induced frequency shift and factor group splitting of the bands due to the intramolecular vibrations were calculated using an intermolecular potential of the atom–atom type. These results show that (1) no phase transition takes place in the crystal under pressure up to 5.5 GPa, (2) the observed pressure-induced frequency shift is mainly caused by the repulsive force between chlorine atoms belonging to the adjacent molecules, and (3) the observed splitting of the bands due to the degenerate intramolecular vibrations is caused by the different intermolecular force acting to the a and b vibrational modes.