  We present the first evidence of a retrograde orbit of the transiting
exoplanet HAT-P-7b. The discovery is based on a measurement of the
Rossiter-McLaughlin effect with the Subaru HDS during a transit of HAT-P-7b,
which occurred on UT 2008 May 30. Our best-fit model shows that the spin-orbit
alignment angle of this planet is \lambda = -132.6 (+10.5, -16.3) degrees. The
existence of such a retrograde planet have been predicted by recent planetary
migration models considering planet-planet scattering processes or the Kozai
migration. Our finding provides an important milestone that supports such
dynamic migration theories.
