  We study semianalytically the gravitational effects on neutrino pair
annihilation near the neutrinosphere and around the thin accretion disk. For
the disk case, we assume that the accretion disk is isothermal and that the
gravitational field is dominated by the Schwarzschild black hole. General
relativistic effects are studied only near the rotation axis. The energy
deposition rate is enhanced by the effect of orbital bending toward the center.
However, the effects of the redshift and gravitational trapping of the
deposited energy reduce the effective energy of the gamma ray bursts' source.
Although each effect is substantial, the effects partly cancel one another. As
a result, the gravitational effects do not substantially change the energy
deposition rate for either the spherical symmetric case or the disk case.
