  We have investigated the electronic structure of A-site ordered
CaCu$_3$Ti$_4$O$_{12}$ as a function of temperature by using angle-integrated
and -resolved photoemission spectroscopies. Intrinsic changes of the electronic
structure have been successfully observed in the valence band region by the
careful consideration of charging effects. The obtained photoemission results
have revealed that the intensity of the nearly non-dispersive Cu 3$d$-O 2$p$
hybridized bands at the binding energy of $\sim$2 eV increases with decreasing
temperature from 300 to 120 K. This suggests that the density of the localized
states, caused by the strong correlation effects, enhances as temperature
decreases.
