  Emission mechanism of the magnetars is still controversial while various
observational and theoretical studies have been made. In order to investigate
mechanisms of both the persistent X-ray emission and the burst emission of the
magnetars, we have proposed a model that the persistent X-ray emission consists
of numerous micro-bursts of various sizes. If this model is correct, intensity
Root Mean Square (RMS) variations of the persistent emission exceed the values
expected from the Poisson distribution. Using $Suzaku$ archive data of 11
magnetars (22 observations), the RMS intensity variations were calculated from
0.2 keV to 70 keV. As a result, we found significant excess RMS intensity
variations from all the 11 magnetars. We suppose that numerous mircro-bursts
constituting the persistent X-ray emission cause the observed variations,
suggesting that the persistent X-ray emission and the burst emission have
identical emission mechanisms. In addition, we found that the RMS intensity
variations clearly increase toward higher energy bands for 4 magnetars (6
observations). The energy dependent RMS intensity variations imply that the
soft thermal component and the hard X-ray component are emitted from different
regions far apart from each other.
