Magnetars, which are highly magnetized neutron stars with field strengths greater than the quantum critical level 4.4*10^13 G, show persistent X-ray emission as well as sporadic bursts. Using Suzaku and HETE-2 data, we discovered that both the persistent X-ray emission and burst spectra consist of thermal (<10 keV; two blackbody function) and hard X-ray (>10 keV; powerlaw) components. We found a temperature correlation for the thermal component as well as a luminosity correlation of these components for 5 orders of magnitude. We have been proposing a model that the persistent X-ray emission consists of numerous micro bursts of various sizes. In our model, intensity RMS variations should be larger than the values expected from the Poisson distribution. We thus calculated the RMS variation for 11 magnetars observed by Suzaku in the soft (0.2-12 keV) and hard (10-70 keV) band. As a result, the RMS variations are significantly greater than the values expected from the Poisson distribution in both energy bands, and they are greater in the hard band than that in the soft band. An overview of previous magnetar observations, and our observational studies on magnetar emissions will be presented.