In order to investigate effects of molecular behavior of water at interface on the rock surface, high temperature-pressure cell (up to 400 °C and 50 MPa) was developed to measure infrared and Raman, which was attached with optical microscopy, therefore, in situ and microscopic measurements were enable at high temperature and pressure conditions. Infrared properties of thin film water and interfacial water at rock surface were measured. As a result of infrared spectroscopic measurements of thin film water, the broad peak at ca. 3360 cm-1 of infrared spectra, attributed to OH stretching mode of water molecular, was observed at room temperature and pressure. Continuous shift of the OH vibration mode was obtained from room to hydrothermal conditions. These results indicate that changes of molecular structure of the water were detected by using newly designed high temperature-pressure cell. Compared with the result of infrared properties of thin film water, infrared properties of interfacial water at rock surface exhibit different trend: the peak position shifted to higher wavenumber with increasing temperature and did not shift with pressure. Molecular structure of interfacial water on the rock and rock-forming mineral at elevated temperatures and pressures were not only changes due to physical conditions such as temperature and pressure but also interaction between interfacial water and solid rock materials.