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