  We present the Suzaku results of the mixed-morphology supernova remnant W28.
The X-ray spectra of the central region of W28 exhibit many bright emission
lines from highly ionized atoms. An optically thin thermal plasma in
collisional ionization equilibrium, either of single-temperature or
multi-temperature failed to reproduce the data with line-like and bump-like
residuals at the Si Lyman$\alpha$ energy and at 2.4--5.0 keV, respectively. The
bumps probably correspond to radiative recombination continua from He-like Si
and S. A simple recombining plasma model nicely fit the bump structures, but
failed to fit low energy bands. The overall spectra can be fit with a
multi-ionization temperature plasma with a common electron temperature. The
multi-ionization temperatures are interpreted as elemental difference of
ionization and recombination timescales. These results prefer the rarefaction
scenario for the origin of the recombining plasma.
