A throttle valve controller achieves high output response to the smaller deviation of the actual opening from the demand opening of the throttle valve and achieves high control stability against the larger deviation. It has a preset data table containing proportional gain values and integral gain values of PID control in correspondence to deviation values in inversely proportional arrangement. During the transitional state of control system, a pair of provisional gain values are read out of the table in response to the deviation value: (step S3), these gain values are compared with those of the previous operation cycle and the smaller gain value pair are selected: (steps S4-S7), and the valve drive signal is calculated from the selected gain values:(steps S8, S11). Consequently, the controller achieves high output response to the smaller deviation due to the larger gain value and high control stability without the overshooting of valve movement against the larger deviation due to the smaller gain value.