  We elaborate masses of open-charm mesons (c\bar{d} and c\bar{s}) with
J^P=0^-,1^-,0^+,1^+ from a viewpoint of ordinary light-heavy systems in the
analysis of standard Borel-transformed QCD sum rule. This analysis is
implemented with the operator product expansion up to dimension 6, permitting
corrections to the order alpha_s and to the order m_s, and without relying on
1/m_c-expansion. The obtained results following our stringent criteria for the
continuum-threshold dependence, the Borel window and the Borel stability,
indicate that the charmed-meson masses in the 0^+ channel are overestimated by
100 \sim 200 MeV in comparison with the experimental data, which were recently
reported as the rather broad state of D^{*+}(2351) and the extremely narrow
state of D_s^{*+}(2317), respectively. Such large mass-discrepancies from the
data cannot be seen in other channels, where conversely our results of the
c\bar{s}-meson masses are even underestimated somewhat in comparison with data,
independent of the value of the strange-quark mass adopted in our calculations.
  From these results, it might be expected that the measured low mass of
D_s^{*+}(2317) is a manifestation of an exotic state with the structures of a
four-quark or a molecule, while at present the D^{*+} is not in conflict with
the existing data due to its large width.
