When throttle valve opening degree is larger than predetermined throttle valve opening degree Y in the case where a decision on shift to gear stage at which maximum load is applied to predetermined rotary member of automatic transmission is made, the gear stage is not formed. Therefore, large load is restrained from being applied to the predetermined rotary member of the automatic transmission. Besides, gear stage that is lower in vehicle speed than the gear stage by one stage or gear stage that is higher in vehicle speed than the gear stage by one stage is formed depending on whether acceleration requirement is large or small. Therefore, driving torque corresponding to the acceleration requirement is likely to be obtained. In consequence, the load applied to the predetermined rotary member of the automatic transmission can be reduced, and feeling of strangeness can be restrained from being caused by the driving torque.

This device for estimating a degree of fatigue of a motive force transmitting component is a device for estimating the degree of fatigue of a motive force transmitting component in a motive force transmitting system from a motor/generator (drive source) to a driving wheel (wheel), and is provided with an estimation unit which estimates the degree of fatigue of the motive force transmitting component on the basis of the magnitude and direction of torque acting on the motive force transmitting component, and an output unit which outputs a signal indicating that the degree of fatigue has exceeded a threshold if the degree of fatigue exceeds a prescribed threshold that is set in advance, wherein the degree of fatigue is estimated by the different methods when the motive force transmitting component is a gear or a shaft.