  Direct detection of dark matter with directional sensitivity has the
potential to discriminate the dark matter velocity distribution. Especially, it
will be suitable to discriminate isotropic distribution from anisotropic one.
Analyzing data produced with Monte-Carlo simulation, required conditions for
the discrimination is estimated. If energy threshold of detector is optimized,
$O(10^3-10^4)$ event number is required to discriminate the anisotropy.
