In a vehicle having a continuously variable transmission, a road surface gradient estimation block for calculating a road surface gradient and a target vehicle speed value decision block for deciding a vehicle speed according to the road surface gradient are provided. During a vehicle running, when the road surface gradient becomes larger than a stored judgment value, a target vehicle speed is prepared in accordance with a vehicle speed at a time a road gradient value exceeds over an establishment value, a transmission ratio is controlled to have the target speed. Accordingly, a drive force in response to the road surface gradient can be carried out without a change-over of a transmission mode by a driver himself.