PURPOSE: To increase easily the luminous intensity on the surface of an original by setting a light transmitting tool having an irradiation surface including a large input surface area opposite to the light source and a small area to be irradiated respectively between the light source and the scan reading point of the original.

CONSTITUTION: A light transmitting tool 10 made of methacrylic resin is set between a fluorescent lamp light source 1 and a scan reading point 3 of an original 2. A hollow light input surface 11 equivalent to the projection area of a light emitting surface is provided to the tool 10 at the side of a light source 1 and opposite to the light emitting surface of the source 1. At the same time, an irradiation surface 12 having an extremely small area compared with the surface 11 is formed at the side of the point 3. Therefore an area of the surface to be irradiated at a place near the point 3 of the original 2 to be irradiated by the illumination light 16 is also small like the surface 12. At the same time, the light 16 is reflected by a white outer circumferential surface 17 of the tool 10 and simultaneously intensified. As a result, the luminous intensity is considerably increased on the original surface to be irradiated.