To immediately and easily recognize the degree of a setting value as a result of rotating operation when a control knob is rotated for changing the setting value for determining the operation content of object equipment.

An incident side light transmission piece 5e of a light transmitting member 5 held by a control knob 3 is extended on the back side of a vessel 1 arranged with the control knob 3 on the front side by fitting to a fitting part 5a, the color of light, which is made incident to a light transmission plate 11 arranged on the back side of the vessel 1, and emitted from the part of a light emission plane 11a facing a light incidence plane 5g of the incident side light transmission piece 5e of the light transmitting member 5, from lamps 7 and 9 of mutually different light emission colors is changed corresponding to a distance between the part of the light emission plane 11a facing the light incidence plane 5g of the incident side light transmission piece 5e and respective light incidence planes 11b and 11c, and the color of bright light of an index window 3c of the control knob 3 or illumination light on a peripheral surface 3b of the control knob 3 is changed corresponding to the rotating position of the control knob 3.