A travel control device for a vehicle, comprising: a steering transmission ratio variable device for installation in a steering transmission system between a steering wheel and steered wheels (19FL, 19FR), and which is configured to change a steering transmission ratio by rotating a lower steering shaft with respect to an upper steering shaft; a steering transmission ratio control device, which is configured to calculate a target value of a relative rotational angle between the upper steering shaft and the lower steering shaft, which is required to achieve a target steering transmission ratio, and to control the steering transmission ratio variable device so that an actual relative rotational angle conforms to the target value; a power steering device for installation in the steering transmission system between the steered wheels (19FL, 19FR) and the steering transmission ratio variable device, and is configured to generate a steering assist torque; a steering assist torque control device, which is configured to calculate a target steering assist torque, and to control the power steering device so that an actual steering assist torque conforms to the target steering assist torque; and a driving support device, which is configured to calculate a target steering angle of the steered wheels (19FL, 19FR) for causing the vehicle to travel along a predetermined travel path, and to correct the target steering assist torque so that an actual steering angle of the steered wheels (19FL, 19FR) conforms to the target steering angle, wherein the steering transmission ratio control device is configured to decrease a magnitude of a change in the relative rotational angle controlled by the steering transmission ratio variable device when the driving support device is in operation compared to when the driving support device is not in operation; characterized in that the steering transmission ratio control device is configured to acquire, when the driving support device starts an operation thereof, a current value of the relative rotational angle, and calculate, when the driving support device is in operation, the target value of the relative rotational angle to be the current value, to thereby cause the change in the relative rotational angle controlled by the steering transmission ratio variable device to be 0. a steering transmission ratio variable device for installation in a steering transmission system between a steering wheel and steered wheels (19FL, 19FR), and which is configured to change a steering transmission ratio by rotating a lower steering shaft with respect to an upper steering shaft; a steering transmission ratio control device, which is configured to calculate a target value of a relative rotational angle between the upper steering shaft and the lower steering shaft, which is required to achieve a target steering transmission ratio, and to control the steering transmission ratio variable device so that an actual relative rotational angle conforms to the target value; a power steering device for installation in the steering transmission system between the steered wheels (19FL, 19FR) and the steering transmission ratio variable device, and is configured to generate a steering assist torque; a steering assist torque control device, which is configured to calculate a target steering assist torque, and to control the power steering device so that an actual steering assist torque conforms to the target steering assist torque; and a driving support device, which is configured to calculate a target steering angle of the steered wheels (19FL, 19FR) for causing the vehicle to travel along a predetermined travel path, and to correct the target steering assist torque so that an actual steering angle of the steered wheels (19FL, 19FR) conforms to the target steering angle, wherein the steering transmission ratio control device is configured to decrease a magnitude of a change in the relative rotational angle controlled by the steering transmission ratio variable device when the driving support device is in operation compared to when the driving support device is not in operation; characterized in that the steering transmission ratio control device is configured to acquire, when the driving support device starts an operation thereof, a current value of the relative rotational angle, and calculate, when the driving support device is in operation, the target value of the relative rotational angle to be the current value, to thereby cause the change in the relative rotational angle controlled by the steering transmission ratio variable device to be 0.