A light-collective member (142) for collecting a light outputted from a light source (140), which irradiates a light toward a document surface, toward a sub-scanning direction is provided in front of the light source (140). An illuminating portion which is so formed that each of opposite end surfaces (170, 172) in the main scanning direction of the light-collective member (142) has an obtuse angle with respect to a bottom surface (174) facing the light source (140).