  We have performed scanning tunneling microscopy and differential tunneling
conductance ($dI/dV$) mapping for the surface of the three dimensional
topological insulator Bi$_{2}$Se$_{3}$. The fast Fourier transformation applied
to the $dI/dV$ image shows an electron interference pattern near Dirac node
despite the general belief that the backscattering is well suppressed in the
bulk energy gap region. The comparison of the present experimental result with
theoretical surface and bulk band structures shows that the electron
interference occurs through the scattering between the surface states near the
Dirac node and the bulk continuum states.
