A power transmission apparatus may include a first input shaft including at least one input gear, a second input shaft, at least one input gear. a first output shaft, more than two speed gears engaged respectively with the at least one input gear, at least one synchronizer operably connecting the more than two speed gears to the first output shaft selectively. a second output shaft, at least one speed gear engaged respectively with the at least one input gear, a reverse speed gear rotatably disposed on the second output shaft, at least one synchronizer operably connecting the at least one speed gear or the reverse speed gear to the second output shaft selectively, an idle shaft, and first and second idle gears fixedly disposed on the idle shaft and engaged respectively to one input gear on the first input shaft and the reverse speed gear.