  We are developing 3 dimensional simulation codes for coalescing binary
neutron stars. A code using the maximal slicing condition is obtained. To
evaluate the gravitational radiation, we implemented a gauge-invariant wave
extraction and compared the wave forms with the metric tensors at the wave
zone. The energy spectrum of the waves was also evaluated to investigate the
possibility that the excitation of the quasi-normal modes of the black hole,
which may be formed after the merger of two stars, can be observed.
