A power transmission apparatus may include: a torque converting device including a first rotation element directly connected to one power source, a second rotation element selectively connected to another power source, and a third rotation element, an input device including a first input shaft directly connected to the third rotation element, selectively connected to the second rotation element, and provided with at least one input gear, and a second input shaft disposed without rotational interference with the first input shaft, selectively connected to the second rotation element, and provided with at least one input gear, a first speed output unit configured to convert toque input from the first input shaft or the second input shaft and output the converted torque, and a second speed output unit configured to convert torque input from the first input shaft or the second input shaft and output the converted torque.