  A time-variability study of the neutral iron line flux at 6.40keV in the Sgr
B2 region from data of Suzaku and Chandra is presented. The highly ionized iron
line at 6.68keV is due to Galactic Center Diffuse X-rays (GCDX), and is thus
time invariable. By comparing the 6.68keV and 6.40keV line fluxes, we found
that the 6.40keV flux from the SgrB2 complex region is time variable;
particularly the giant molecular cloud M0.66-0.02, known as ``Sgr B2 cloud'' is
highly variable. The variability of the 6.40keV line in intensity and spatial
distribution strongly supports the scenario that the molecular clouds in the
SgrB2 region are X-ray Reflection Nebulae irradiated by the Galactic Center
(GC) black hole Sgr A*.
