A planetary gear train of an automatic transmission may include: a first input shaft; a second parallel shaft; a compound planetary gear set on the second shaft, and including a first rotation element engageable with the first shaft through two paths respectively having an external gear, a second rotation element connected to an output gear so as to be operated as an output element, a third rotation element engageable with the first shaft through one path having an external gear and selectively fixed, and a fourth rotation element engageable with the first shaft through one path having an external gear and selectively fixed; four transfer gears forming the external gears; frictional elements including clutches selectively connecting the first, third, and fourth rotation elements to the first shaft and brakes selectively connecting the third and fourth rotation elements to a transmission housing.