Detection outputs value based on outputs of a sensor for detecting a depressed position of a pedal are input via the input section; meanwhile, a detection output value corresponding to a non-depressed state of the pedal is set as an offset value. The detection output value, input via the input section, is adjusted with the offset value, so as to provide an adjusted detection output value corresponding to an actual depressed amount of the pedal. The adjusted detection output value is converted into a control value corresponding to the depressed amount of the pedal. Thus, the offset value is variably set in accordance with an individual difference, aging, etc. of the pedal, so that the detection output value adjusted with such an offset value can be a value having unevenness in the sensor outputs, which may have occurred due to an individual difference, aging, etc. of the pedal, automatically compensated.