PURPOSE: To have distinct indication of characters and symbols on a switch display part by forming a control button from an inner cap arranged near the lamp and an outer cap having a hole for forming a display part, and embedding color generating substance with transparency in this hole.

CONSTITUTION: An approx. transparent resin such as polycarbonate and an oblique resin such as black ABC are used for an inner 2 and an outer cap 3, respectively, of a control button 1. To provide these inner and outer caps 2, 3 with a certain wall thickness, the inner one 2 is equipped with a protrusion 20 so as to be mating with the shapes of characters and numerical figures on the display part 5, and an adjustment is made so that the thickness of color generating substance 18 does not exceed a certain value. As this color generating substance 18 is used an ink 18 with desired color, which is applied to a hole part 7. This accomplishes a switch illuminating construction, which enables distinct reading of characters and symbols on the display part of switch whether it is in daytime or at night.