  We present an X-ray analysis on the Galactic supernova remnant (SNR)
G298.6-0.0 with Suzaku. The X-ray image shows a center-filled structure inside
the radio shell, implying this SNR is categorized as a mixed-morphology (MM)
SNR. The spectrum is well reproduced by a single temperature plasma model in
ionization equilibrium, with a temperature of 0.78 (0.70-0.87) keV. The total
plasma mass of 30 solar mass indicates that the plasma has interstellar medium
origin. The association with a GeV gamma-ray source 3FGL J1214.0-6236 on the
shell of the SNR is discussed, in comparison with other MM SNRs with GeV
gamma-ray associations. It is found that the flux ratio between
absorption-corrected thermal X-rays and GeV gamma-rays decreases as the MM SNRs
evolve to larger physical sizes. The absorption-corrected X-ray flux of
G298.6-0.0 and the GeV gamma-ray flux of 3FGL J1214.0-6236 closely follow this
trend, implying that 3FGL J1214.0-6236 is likely to be the GeV counterpart of
G298.6-0.0.
