A vehicle interior illumination lamp 11 for mounting in an opening formed in an interior member of a vehicle includes a function portion 12 having a bulb 22 serving as a light source and a switch lever 74 for effecting and interrupting the supply of electric power to the bulb 22, and a design portion 13 having a cover lens 42 covering the function portion 12 and a switch knob 47 for operating the switch lever 74. The switch lever 74 is pivotally mounted on the function portion 12, and the switch knob 47 is pivotally mounted on the design portion 13. When the function portion 12 and the design portion 13 are combined together, shaft portions 78, serving as an axis of pivotal movement of the switch lever 74, coincide with shaft portions 84 serving as an axis of pivotal movement of the switch knob 47.