A power transmission apparatus for a vehicle may include a first input shaft selectively connectable to an engine output shaft, a second input shaft coaxial and selectively connectable to the first input shaft, a torque mediating shaft coaxial with the first input shaft, a first intermediate shaft in parallel with the first input shaft, a compound shifting section including a first planetary gear set having a sun gear fixed to the torque mediating shaft, a planet carrier fixed to the second input shaft, and a ring gear and a second planetary gear set having a sun gear fixedly to the first intermediate shaft, a ring gear selectively connectable to a transmission housing, and a planet carrier for outputting a torque, and a fixed shifting section receiving a torque from the compound shifting section and outputting a modified torque to the second sun gear of the compound shifting section.