アブストラクト：
We analyzed the 4.7 micron CO absorption band in nearby 47 infrared galaxies using observations of AKARI. Many of the sample showed large-columns (logNH~23) of warm (several x 100 K) gas probably heated by X-ray from AGNs. We found that AGN-starburst composites showed on average larger column densities than Seyfert 2s. This result suggests that the obscuration by an AGN torus is also effective in a composite and that the torus is geometrically thicker than that in a typical Seyfert. This difference may possibly reflect the AGN-starburst connection that supernovae in a circum-nuclear disk assist the formation of a thick torus.