A planetary gear train may include input shaft, output shaft, first planetary gear set disposed on the input shaft and including first rotation element selectively connected to the input shaft or transmission housing, second rotation element selectively connected to the input shaft or the transmission housing, and third rotation element connected to the output shaft, second planetary gear set disposed on the output shaft and including fourth rotation element selectively connected to the input shaft and connected to the first rotation element, fifth rotation element connected to the third rotation element and directly connected to the output shaft, and sixth rotation element selectively connected to the input shaft, three transfer gears, and six frictional elements including four clutches selectively connecting the first, second, fourth, and sixth rotation elements to the input shaft and two brakes selectively connecting the first and second rotation elements to the transmission housing respectively.