  Revealing what fraction of galaxies harbor AGN is central in understanding
black hole accretion history of the Universe. However, optical and soft X-ray
surveys miss the most highly obscured AGNs. Infrared (IR), instead, is more
robust against absorption. Previous IR photometric surveys, however, only had 4
or 5 filters in mid-IR. Our AKARI North Ecliptic Pole (NEP) wide field sample
has 18 filters in mid-IR (9 from AKARI, 4 from WISE, and 5 from Spitzer), for
the first time, allowing a sophisticated mid-IR SED fitting diagnosis for a
statistical number of sources (89178 over 5.4 deg$^2$). By using a SED fitting
technique, we investigate the evolution of AGN fraction as a function of
redshift and IR (8-1000 $\mu$m) luminosity in an extinction-free way. We found
that the AGN fraction (F$_{\rm AGN}$) shows no sign of strong redshift
evolution. Instead, F$_{\rm AGN}$ increases with increasing IR luminosity in
all redshifts bins ($0<z<2$).
