The transmission control unit includes a gear ratio abnormality determination unit and a limp home control unit. The gear ratio abnormality determination unit is configured to determine that a gear ratio is abnormal when, during travelling at a predetermined gear position, a difference between an actual gear ratio, which is calculated based on a transmission input shaft rotation speed and a transmission output shaft rotation speed, and a set gear ratio at the predetermined gear position is equal to or greater than a set value. The limp home control unit is configured to, when the gear ratio abnormality determination unit determines that the gear ratio is abnormal, output a disengagement instruction for disengaging all of the plurality of friction elements, when it is confirmed that a neutral state is shifted to according to the output of the disengagement instruction, determine engagement/disengagement of a specific friction element among the plurality of friction elements based on rotation/stop information of a rotation member of the stepped transmission mechanism, and determine an evacuation gear position based on determination information on the engagement/disengagement of the specific friction element, and shift the gear position to the determined evacuation gear position.