The Japanese infrared satellite, AKARI, had a unique capability of the near-infrared spectroscopy at the wavelength 2.5 - 5 micron. AKARI also performed the all-sky survey in the mid- and far-infrared. These data are very useful to study Active Galactic Nuclei (AGNs) from low-z to high-z universe. For the low-z universe, we searched for AGNs which are elusive in other wavelengths. Our search detected hot dust component of the temperature ~ 600 K in normal galaxies. The reasonable explanation is the presence of buried AGNs due to dust. For the high-z universe, AKARI traced rest-frame optical and near-infrared spectra of AGNs at z>4. Using the result, we discussed the evolution of AGNs.
