Abstract: An operating device having a rotary knob capable of rotation operations exhibits compatibility between speed and precision in operation and does not require use of a plurality of rotary knobs. In the operating device (1) including the rotary knob (4) and the rotation detecting means (8) for detecting the rotated angle of the rotary knob, the rotary knob includes a small-diameter component (4F) for operating the rotary knob quickly, and a large-diameter component (4S) for operating the rotary knob slowly or for fine adjustment, and the determining means (9) is provided for determining the rotated position of the rotary knob when the rotary knob is operated.