To make rising characteristics fast and to enhance the availability of light in the case of using a small-diameter reflection type cold cathode lamp.

This device is equipped with a reflection type cold cathode lamp 16 provided with a valve 17 having irradiation directivity by forming a mainly reflecting insulating reflection film 18 on a part of an inner wall surface, a heater 20 provided on the outer peripheral surface of the valve 17 corresponding to only a part of the area of the reflection film 18, and a casing 21 made of heat-resistant and white resin having a reflection surface 22 to cover the reflection surface 18 and the heater 20 side of the valve 17. Thus, by energizing and properly heating the heater 20, the lamp 16 emits light in a quick rising characteristic state even when it is used under low temperature environment. The light radiated from the lamp 16 is partially transmitted through the reflection film 18. Since the heater 20 exists only at a part of the area of the reflection film 18, the light transmitted through the reflection film 18 and the valve 17 without being intercepted by the heater 20 is reflected on the reflection surface 22, so that the utilization efficiency of light is enhanced.