A planetary gear train of an automatic transmission includes: a first torque-receiving shaft; a second shaft parallel with the first shaft; a first planetary gear set on the first shaft having a first, second and third rotation elements operated as a fixed or output element, directly connected to the first shaft and operated as an input element, and operated as a selective output element, respectively; a compound planetary gear set including a second planetary gear set and a third planetary gear set, and having a fourth, fifth, sixth and seventh rotation elements, selectively connected to the second and third rotation elements, connected to an output gear, selectively connected to the first rotation element, and selectively connected to the third rotation element, respectively; three transfer gears forming externally-meshed gears; and frictional elements selectively interconnecting the rotation elements or selectively connecting the rotation elements to a transmission housing.