  Oxygen $K$-edge X-ray absorption spectroscopy measurements were conducted on
T*-type La$_{1-x/2}$Eu$_{1-x/2}$Sr$_x$CuO$_4$ (LESCO) to estimate the hole
density ($n_{\rm h}$) and investigate the oxidation annealing effect on $n_{\rm
h}$. A drastic increase in $n_{\rm h}$ due to annealing was found. The increase
in $n_{\rm h}$ cannot be explained solely by the oxygen gain due to annealing,
suggesting that delocalized holes are introduced into the CuO$_2$ plane. A
phase diagram of LESCO was redrawn against $n_{\rm h}$.
