A transmission for an electric vehicle may include an input shaft connect with a motor; a planetary gear set having a first rotation element directly connected to the input shaft, a second rotation element and a third rotation element; an output shaft having an output gear; a first drive gear provided in the third rotation element of the planetary gear set; a first driven gear disposed at the output shaft to be rotatable to engage with the first drive gear; a second drive gear connected to or disconnected from the input shaft; a second driven gear engaged with the second drive gear and directly connected to the first driven gear; a third drive gear directly connected to the second rotation element of the planetary gear set; and a third driven gear engaged with the third drive gear and directly connected to the output shaft.