The invention improves the driveability of a vehicle by controlling a target engine speed according to an engine load and a vehicle running condition to ensure an actual engine speed. In controlling a speed ratio of a continuously variable transmission, an adaptation factor is used for deciding a target engine speed, the adaptation factor is determined according to constants, an average engine load and an average vehicle speed change quantity. Even when the average engine load changes because of fluctuation in an accelerator opening, various running modes can be decided by the adaptation factor depending upon both the average engine load and the average vehicle speed change quantity, thereby improving driveability upon changing speed of the continuously variable transmission.