  Recent observations suggest the presence of supermassive black holes at the
centers of many galaxies. The existence of intermediate-mass black holes
(IMBHs) in globular clusters has also been predicted. We focus on gravitational
lensing as a new way to explore these entities. It is known that the mass
distribution of a self-gravitating system such as a globular cluster changes
greatly depending on the presence or absence of a central massive object. After
considering possible mass distributions for a globular cluster belonging to the
Milky Way galaxy, we estimate that the effect on the separation angle of
gravitational lensing due to an IMBH would be of milliarcsecond order.
