A transmission for electric vehicles may include a first input shaft receiving a rotational force from a first motor; a second input shaft receiving a rotational force from a second motor; a one-way clutch mounted between the first and second input shafts, transferring only a forward rotation of the first input shaft to the second input shaft, and transferring only a reverse rotation of the second input shaft to the first input shaft; an output shaft disposed in parallel to the first and second shafts; a gear shifting device coupled to the first input shaft and the output shaft and coupled to the second input shaft and the output shaft, wherein the gear pairs have different shift ratios, and a gear pair corresponding to a driving speed is selected by a clutch device; and an idler gear coupled between gears coupled to the second input shaft and the output shaft.