The thermal anomaly and molecular motion of tetramethylsilane (TMS) confined in a metal-organic framework, [Zn4O(O2CC6H4CO2)(3)](n) (IMOF-1), have been examined by differential thermal analysis and solid-state wide-line H-1 NMR. Endothermic peaks were observed at 198 and 227 K, which were attributed to the disordered intermediate phase and molten phase, respectively, employing the temperature dependence of H-1 NMR line width. This result suggests an elevation of the melting point of TMS confined in IRMOF-1.