  We present results of three dimensional numerical simulations of the merger
of unequal-mass binary neutron stars in full general relativity. A $\Gamma$-law
equation of state $P=(\Gamma-1)\rho\epsilon$ is adopted, where $P$, $\rho$,
$\varep$, and $\Gamma$ are the pressure, rest mass density, specific internal
energy, and the adiabatic constant, respectively. We take $\Gamma=2$ and the
baryon rest-mass ratio $Q_M$ to be in the range 0.85--1. The typical grid size
is $(633,633,317)$ for $(x,y,z)$ . We improve several implementations since the
latest work. In the present code, the radiation reaction of gravitational waves
is taken into account with a good accuracy. This fact enables us to follow the
coalescence all the way from the late inspiral phase through the merger phase
for which the transition is triggered by the radiation reaction. It is found
that if the total rest-mass of the system is more than $\sim 1.7$ times of the
maximum allowed rest-mass of spherical neutron stars, a black hole is formed
after the merger irrespective of the mass ratios. The gravitational waveforms
and outcomes in the merger of unequal-mass binaries are compared with those in
equal-mass binaries. It is found that the disk mass around the so formed black
holes increases with decreasing rest-mass ratios and decreases with increasing
compactness of neutron stars. The merger process and the gravitational
waveforms also depend strongly on the rest-mass ratios even for the range $Q_M=
0.85$--1.
