A transmission control device includes even-numbered and odd-numbered transmission gears selected via a shift mechanism and causes the torque capacities of two clutches to be transitioned to a certain proportion until the clutch rotation speed difference of a low-speed gear-side clutch reaches 0 or approximately 0, sets the torque capacity of the clutch on the low-speed gear side to be the total torque capacity of both clutches, and sets the torque capacity of the clutch on the high-speed gear side to 0. The heat load on the clutch at the time when the vehicle starts to move is reduced and the durability thereof is improved, and the clutch can be made smaller and lighter.