A power train for an electric vehicle may include an input shaft to which a motor is fixedly connected; a driving gear rotatably mounted on the input shaft; an output shaft disposed in parallel to the input shaft; a driven gear fixed to the output shaft and gear-engaged with the driving gear; a planetary gear set including first, second and third rotation elements wherein the first rotation element is fixedly connected to the input shaft and the second rotation element is fixedly connected to the driving gear, and the third rotation element is restrained from rotating; a friction clutch configured for selectively connecting the input shaft to the driving gear and configured for selectively connecting the input shaft to the driving gear; and a restraining device provided to the third rotation element to implement two states so that only one-way rotation of the third rotation element of the planetary gear set is restrained or two-way rotation thereof is restrained.