A planetary gear train of an automatic transmission may include: a first shaft; a second shaft parallel with the first shaft; a first gear set on the first shaft including a first element selectively connected to the first shaft, a second element selectively connected to the first shaft and a transmission housing, and a third element; a second gear set on the second shaft including a fourth element operably connected to the first element and selectively connected to the first shaft, a fifth element connected to the third element and directly connected to an output gear, and a sixth element selectively connected to the first shaft and selectively connected to the housing; three transfer gears; and frictional elements including clutches selectively connecting the first shaft to elements of the first and second gear sets and brakes selectively connecting elements of the first and second gear sets to the housing.