Disclosed is a power transmission apparatus for a wind generator having an electric generator connected to an apparatus rotor by a main shaft. The electric generator includes a generator rotor and a generator stator. The electric generator may be assembled to the main shaft via the generator rotor, but the generator stator is not assembled to the main shaft. Instead, the generator stator is connected to a stator housing fixed to bearing housings respectively provided on a pair of bearings disposed on an outer surface of a rotor bearing. The rotor bearing is disposed perpendicular to a vertical rotor frame, is formed integrally with the generator rotor, and is connected to an outer surface of the main shaft. The apparatus permits the generator stator to be assembled with a circumference of the generator rotor. The apparatus provides increased convenience and efficiency in assembly.