A revolution rate sensor configured to detect a revolution rate of a first input shaft and an ECU configured to estimate the revolution rate of the first input shaft using another method which is not based on detection of the revolution rate sensor are provided, and the ECU performs engagement permission determination of a switching mechanism associated with the lowest shift stage in first engagement switching mechanisms using an estimated value of the revolution rate of the first input shaft estimated by the ECU when it is determined that a revolution rate of the first input shaft cannot be detected normally by the revolution rate sensor.