  Gravitational Microlensing has been used as a powerful tool for astrophysical
studies and exoplanet detections. In the gravitational microlensing, we have
two images with negative and positive parities. The negative-parity image is a
fainter image and is produced at a closer angular separation with respect to
the lens star. In the case of a red-giant lens star and large impact parameter
of lensing, this image can be eclipsed by the lens star. The result would be
dimming the flux receiving from the combination of the source and the lens
stars and the light curve resembles to an eclipsing binary system. In this
work, we introduce this phenomenon and propose an observational procedure for
detecting this eclipse. The follow-up microlensing telescopes with lucky
imaging camera or space-based telescopes can produce high resolution images
from the events with reddish sources and confirm the possibility of blending
due to the lens star. After conforming a red-giant lens star and source star,
we can use the advance photometric methods and detect the relative flux change
during the eclipse in the order of $10^{-4}-10^{-3}$. Observation of the
eclipse provides the angular size of source star in the unit of Einstein angle
and combination of this observation with the parallax observation enable us to
calculate the mass of lens star. Finally, we analyzed seven microlensing event
and show the feasibility of observation of this effect in future observations.
