A planetary gear train of an automatic transmission for a vehicle may include an input shaft receiving torque of an engine, an output shaft outputting changed torque of the engine, a first planetary gear set, a second planetary gear set, a third planetary gear set, a fourth planetary gear set, a first rotation shaft selectively connected to a transmission housing, a second rotation shaft, a third rotation shaft selectively connected to the transmission housing, a fourth rotation shaft directly connected to the input shaft, a fifth rotation shaft, a sixth rotation shaft selectively connected to the second and fourth rotation shafts, a seventh rotation shaft selectively connected the second rotation shaft, an eighth rotation shaft selectively connected to the seventh rotation shaft, and directly connected to the output shaft, and six friction elements disposed to selectively connect the rotation shafts and selectively connect the rotation shafts with the transmission housing.