Abstract: A rotatable control knob for actuating a rotary switch includes a slit serving as a pointer display element. An illuminating portion of a light guiding unit attached to the control knob is disposed in the slit. A strip light-guiding portion extends spirally from the illuminating portion is secured to the inner surface of the control knob. Thus, light emerging from a planar light-emitting unit disposed under the control knob is incident on the lower surface of the strip light-guiding portion and is guided through the strip light-guiding portion to the illuminating portion. This allows the illuminating portion illuminated with high intensity in the slit so as to function as an indicator.