PURPOSE: To increase the degree of lumimous intensity without burning the readin object, by irradiating the light from the illuminating light source for optical readin on the object after a plurality of refletions by means of the mirror transmitting only infrared rays.

CONSTITUTION: The illuminating light source for optical readin is constituted with the light emission system 20 cnsisting of the halogen lamp 1 and the cold mirror 2 which transmits infrared rays and reflects other lights. The radiant lights from this light emission system irradiate the document surface 10 while reducing the infrared ray components through being reflected in the reflection optical path consisting of cold mirrors C1∼Cn of a plurality alternately arranged.