X-ray reflection mirror of the Soft X-ray Telescope onboard ASTRO-H was coated by gold thin layer. Gold have M-shell X-ray absorption edge around 2 keV which is included in the energy band covered with the focal plane detector such as Soft X-ray Imager and Soft X-ray Spectrometer. It is important to make response function taken int account the Au M-dege structure especially for the Soft X-ray Spectrometer because It has unprecedented high energy resolution of 5 eV from 0.3 to 12 keV. We performed the detailed measurements of of reflectivity of the mirror using reflectometer in the synchrotron radiation facility KEK PF BL-11B from Nov. 29, 2011 to Dec. 5. X-ray beam of BL-11B was monochromatized to E/deltaE of 5000 by Double crystal monochromator using Si(111). We obtained the reflectivity at the grazing incident angles of 1.0, 1.2, and 1.4 degrees. While the energy pitch was set to be 2 eV in the 2.1-4.1 keV band, the reflectivity in the 2.2-2.35 keV band was also measured in detail with the energy pitch of 0.25 eV. We report the results and optical parameters of the SXT mirror such as reflectivity, and roughness calculated from the measurements.