An output shaft of an automatic transmission is constituted by a first output shaft outputting a driving force from a gear train of an automatic transmission and a second output shaft connected to the first output shaft so as to be movable in an axial direction and to be fixed in a rotational direction with respect to the first output shaft. The second output shaft is integral with a parking gear which fixes the second output shaft in rotation when the automatic transmission is set at a parking position. This arrangement improves applicability to the change of a longitudinal dimension of an automatic transmission and suppresses vibrations from being inputted from driving wheels to a gear train.