A transmission for a vehicle may include a first input shaft selectively receiving power from an engine, a second input shaft continuously receiving power from the engine, a first output shaft and a second output shaft disposed in parallel to the first input shaft and the second input shaft, respectively, a first shift device configured to make a series of desired gear shift ranges between the first input shaft and the and the first output shaft and between the first input shaft and the second output shaft, and a second shift device configured to make duplicate gear shift ranges, which have a gear ratio identical to a gear ratio of one or more gear shift ranges of the series of gear shift ranges made by the first shift device, using the second input shaft.