The rotational motions in hydrophobic hydration of benzene were examined over a wide range of temperature, in order to detect changes in the dynamical environment of the solute in a supercooled aqueous solution and a clathrate hydrate. Combined with the capillary method, NMR spin-lattice relaxation time measurements were performed to obtain the reorientational relaxation time of benzene in water asa function of temperature. A clathrate hydrate of the smallest aromatic molecule was formed without high pressure or help gas. It is found that the guest benzene molecule reorients 3 times faster with a smaller friction in a clathrate hydrate at a lower temperature than in a supercooled solution at a higher temperature. Correspondingly, the activation energy for the reorientation of the guest benzene molecule is found to be smaller in the clathrate hydrate. These findings show how sensitively the rotational motions reflect structural changes in the hydration shell.