A driving amount controller for reducing a response delay or erroneous deviation in control of a driving amount of a controlled system. The driving amount controller includes an ECU that increases an add-in amount to a duty ratio DUT of a control signal according to an increase in the speed variation ΔDTHR of a target opening DTRH of the throttle valve 16 when the speed variation ΔDTHR is positive. In addition, the ECU increases the add-in amount to the duty ratio DUT of the control signal according to a decrease in the speed variation ΔDTHR when the speed variation ΔDTHR is negative. A throttle valve on a vehicle is an example of the controlled system.