  We investigate how central black holes (BHs) inhabited in galactic dark halos
could affect strong gravitational lensing. The distribution of integral lensing
probability with image separations are calculated for quasars of redshift 1.5
by foreground dark matter halos. The mass density of dark halos is taken to be
the Navarro-Frenk-White (NFW) profile such that, when the mass of a halo is
less than $10^{14} M_{\sun}$, its central black holes or a bulge is included as
a point mass. The relationship between the masses $M_{\bullet}$ of supermassive
black holes and the total gravitational mass $M_{\mathrm{DM}}$ of their host
galaxy is adopted from the most recent literature. Only a flat $\Lambda$CDM
model is considered here. It is shown that, while a single black hole for each
galaxy contributes considerable but not sufficient lensing probabilities at
small image separations compared with those without black holes, the bulges
(which are about 100--1000 times larger in mass than a typical black hole)
would definitely contribute enough probabilities at small image separations,
although it gives too high probabilities at large separation angles compared
with lensing observations.
