PURPOSE: To provide contact image sensor which can easily perform assembly with high accuracy and can provide sharp images as a result.

CONSTITUTION: Concerning this image sensor provided with a sensor array 3 corresponding to the read width of an original, light source array 4A and 4B for irradiating the original with light, rod lens array 2 for forming the image of reflected light from the original to the sensor array, and left and right housings 21A and 21B for forming a groove where this rod lens array is arranged, the sensor array 3 and the rod lens array 2 are fitted to only one of the left and right housings 21A and 21B.