A powertrain for an electric vehicle may include a motor, a planetary gear set including at least two sun gears, a three-stage pinion having three different diameters and provided as a planetary gear, a planet carrier provided as a rotation axis of the planetary gear and directly connected to a differential case of a differential device, and a ring gear fixed to a transmission housing, and at least two clutches provided to selectively transmit power of the motor to the sun gears of the planetary gear set.