To provide a switch integrated type illuminating device of small size which is hard to fail and has high reliability.

An illuminating device 10 includes contacts 23, 24 which are electrically connected to an LED 22 in a light source module 20, contacts 43, 44, 53, 54 of relay terminals 40, 50 provided in a slide type switch knob 30, and contacts 71a, 72a, 73a of bus bars 71 to 73 provided in a lower case 60. The contacts 71a, 72a, 73a are electrically connected to external connection terminals 71b, 72b, 73b. The switch knob 30 is freely slidably attached to the lower case 60, and the contacts 23, 24 are electrically connected to the contacts 71a, 72a, 73a via the contacts 43, 44, 53, 54 in accordance with the slide position of the switch knob 30. Contacts 23, 24, 43, 44, 53, 54, 71a, 72a, 73a are each arranged to overlap each other in the thickness direction of the lower case 60.