Adsorption isotherms of o-xylene on Spheron 6, a graphitized carbon black, are obtained at various temperatures using a quartz beam microbalance. BET plots are made to estimate the molecular area of o-xylene from these isotherms. On Spheron 6, the molecular area of o-xylene (m.p $-25^{circ}C$) remains constant until the temperature is increased up to $-15^{circ}C$, but increases abruptly between $-15^{circ}C$ and $-14^{circ}C$, and then again remains constant thereafter. These results are interpreted as implying that the adsorbed o-xylene molecules are flatly localized on Spheron 6 with compact packing below $-15^{circ}C$ while they gain a rotational degree of freedom around the benzene ring at the higher temperature.