A light source lamp socket of an image reader is formed to be capable of being placed as close to a platen glass as possible to increase the intensity of light beams to be irradiated on a original. A part of each of lamp socket attached on the both ends of a lamp tube of a light source lamp, which faces a platen glass, is cut-away into the shape of one or more flat surfaces such that a part of the lamp tube is exposed from a part of such a flat portion. Therefore, the light source lamp can be move closer to the platen glass a distance corresponding to the depth of the cut-away section of the lamp socket.