We performed the deepest search for an X-ray emission line between 0.5 and 7 keV from
non-baryonic dark matter with the Suzaku XIS. Dark matter associated with the Milky Way
galaxy was selected as the target to obtain the best signal-to-noise ratio. From the
Suzaku archive, we selected 187 data sets of blank sky regions which were dominated by
the X-ray diffuse background. I will explain how we can reach the deepest search with
Suzaku with Look Elsewhere Effect (LEE) correction. The 3 sigma upper limit for the
emission line intensity between 1 and 7 keV was ~ 0.01 photons /cm2/ s/str.