To provide an operating knob for a rotary electronic device preventing from erroneous operation.

For the operating knob 4 of the rotary electronic device 3 with a tip of its rotary shaft arranged at the rear of through-holes 2a provided at a case 2 of the electronic device, a non-circular concave part or a convex part is provided at the tip of the rotating shaft, and a convex part or a concave part for insertion-coupling with the above concave part or the convex part is provided at a tip of the shaft integrally formed with the operating knob 4, so that the operating knob 4 can be free in insertion into and removal from the rotating shaft of the rotary electronic device 3. The concave part or the convex part provided at the tip of the rotating shaft is to be of a regular hexagon.