A powertrain for a vehicle may include a compound planetary gear set configured such that, of four rotation elements, a first rotation element is connected to an input shaft and a second rotation element is connected to an output element; a brake provided to connect a rotating body to a transmission housing to be locked thereto; a first clutch device provided to switch a connection state of the rotating body between a third rotation element and a fourth rotation element of the compound planetary gear set; and a second clutch device provided to switch a connection state of the second rotation element of the compound planetary gear set to the input shaft.