The X-ray emission from the supernova remnant N23 are studied using the X-ray Imaging Spectrometer (XIS) onboard Suzaku. Owing to superior energy resolution of the XIS, we obtained a H-like and He-like Ka emission line spectrum of Oxygen with unprecedentedly high quality. As a result, we identified a new thin thermal spectra component which can be represented with Non-Equilibrium Ionization model with a temperature ~0.2keV, as well as that with a temperature of ~0.5keV so far as known. This alters the estimate of the ionization timescale net from ~ 10~(11)cm~(-3) s to ~ 10~(13)cm~(-3)s, thereby identifying N23 as an old SNR, rather than a young SNR(~3800 yr) as believed so far.
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