An illumination switch device comprising: a manipulation knob having a body and an illuminating portion; a hollow slider, which is incorporated into the manipulation knob and is formed of a light shielding material, the slider having a locking claw; a casing which elevatably guides the slider; a switch element which is operated by the elevation movement of the slider; and a light source which irradiates light to a rear surface of the manipulation knob via an inner space of the slider, wherein a front end portion of the slider is disposed so as to protrude forward from the casing and the manipulation knob is snap-connected to the front end portion of the slider protruding from the casing, wherein the manipulation knob includes: a skirt portion which protrudes backward from a peripheral edge portion of the body so as to surround the front end portion of the slider; a connection piece which protrudes backward from a rear surface of the body more than the skirt portion so as to be inserted into the slider; and a locking hole which is provided in the connection piece so as to be located on the lower side of the skirt portion, and to which the locking claw is snap-connected, characterized in that the manipulation knob has a light shielding portion provided on the front outer surface of the body, formed of a light transmitting material, except for said illumination portion, and said locking claw is provided on an inner wall surface of the slider. so as to be inserted into the slider; and locking hole which is provided in the connection piece so as to be located on the lower side of the skirt portion, and wherein an inner wall surface of the slider is provided with a locking claw which is snap-connected to the locking hole. a manipulation knob having a body and an illuminating portion; a hollow slider, which is incorporated into the manipulation knob and is formed of a light shielding material, the slider having a locking claw; a casing which elevatably guides the slider; a switch element which is operated by the elevation movement of the slider; and a light source which irradiates light to a rear surface of the manipulation knob via an inner space of the slider, wherein a front end portion of the slider is disposed so as to protrude forward from the casing and the manipulation knob is snap-connected to the front end portion of the slider protruding from the casing, wherein the manipulation knob includes: a skirt portion which protrudes backward from a peripheral edge portion of the body so as to surround the front end portion of the slider; a connection piece which protrudes backward from a rear surface of the body more than the skirt portion so as to be inserted into the slider; and a locking hole which is provided in the connection piece so as to be located on the lower side of the skirt portion, and to which the locking claw is snap-connected, a skirt portion which protrudes backward from a peripheral edge portion of the body so as to surround the front end portion of the slider; a connection piece which protrudes backward from a rear surface of the body more than the skirt portion so as to be inserted into the slider; and a locking hole which is provided in the connection piece so as to be located on the lower side of the skirt portion, and to which the locking claw is snap-connected, characterized in that the manipulation knob has a light shielding portion provided on the front outer surface of the body, formed of a light transmitting material, except for said illumination portion, and said locking claw is provided on an inner wall surface of the slider. so as to be inserted into the slider; and locking hole which is provided in the connection piece so as to be located on the lower side of the skirt portion, and wherein an inner wall surface of the slider is provided with a locking claw which is snap-connected to the locking hole.