A control device and a control method capable of eliminating a torque variation in changing an air/fuel ratio and establishing a compatibility of promotion in fuel economy with promotion in drivability is provided. The device includes an outer environment detector for detecting an outer environment in running a vehicle, a running environment determining device for predicting a current running environment in accordance with the outer environment, a data storage device for storing data for changing a driving characteristic, a selecting device for selecting the data, a control quantity calculator for calculating a control quantity based on the data, and a control actuator for controlling a control object. The engine output is efficiently utilized since the air/fuel ratio is changed in accordance with the change in the running environment, and the fuel cost reduction and the promotion of the drivability can be achieved since the selecting of the air/fuel ratio is performed in accordance with the running environment.