  We present the analysis of Suzaku observations of the young open cluster
Westerlund 2, which is filled with diffuse X-ray emission. We found that the
emission consists of three thermal components or two thermal and one
non-thermal components. The upper limit of the energy flux of the non-thermal
component is smaller than that in the TeV band observed with H.E.S.S. This may
indicate that active particle acceleration has stopped in this cluster, and
that the accelerated electrons have already cooled. The gamma-ray emission
observed with H.E.S.S. is likely to come from high-energy protons, which hardly
cool in contrast with electrons. Metal abundances of the diffuse X-ray gas may
indicate the explosion of a massive star in the past.
