A planetary gear train of an automatic transmission for a vehicle may include an input shaft, an output shaft, three planetary gear sets, three transfer gears, and six friction elements. Each of the three planetary gear sets may include three rotation elements, constituting nine rotational elements. The rotational elements may be connected or selectively connected to the input shaft, a transmission housing or each other by an external gear or by the six friction elements. The three transfer gears may be applied to the external gear.