Adaptive cruise control method improves traveling performance and stoppage maintenance performance on an incline. During adaptive cruise control, a gradient of a road is estimated based on a vehicle acceleration and longitudinal acceleration to enable compensation of a resistance torque with respect to the gradient of the road, which prevents deterioration of a traveling speed of a vehicle on an incline. Also, compensating for a brake torque to prevent the vehicle from being pushed rearward when the vehicle stops or starts to go on an incline may prevent deterioration of performance on an incline.