We developed a software package entitled "SuperCritical for Windows^®" that is used for the thermochemical calculation of reactions between minerals and hydrothermal solutions in the temperature and pressure ranges of 0 to 1000°C and 1 to 5000bars, respectively. This package uses the databases of SUPCRT92 developed by Johnson et al. (1992)., however, the source code is newly encoded with Microsoft^® Visual Basic^® to be more suitable for the present PC environment and more user-friendly compared with SUPCRT92. This software package is composed mainly of two parts: one is for the calculation of the Gibbs energy of formation for minerals, fluids and aqueous species, and the other is for the calculation of the Gibbs energy of reactions among them. The output files are avilable as a text file in the CSV form or a worksheet (xis file) of Microsoft® Excel in order to facilitate the data processing and presentation of the calculation results.