An image reading apparatus has a light source unit for illuminating an object to be illuminated, a reading unit for reading the object illuminated by the light source unit, a reflective unit, having at least a first reflection mirror, for reflecting reading light reflected by the object toward the reading unit, and a first light blocking portion for partially blocking light except the reading light. The first reflection mirror has a reflecting surface for reflecting the reading light, and an end surface substantially orthogonal to the reflecting surface. The first light blocking portion extends in a longitudinal direction of the first reflection mirror toward the end surface of the first reflection mirror, with a tip end of the first light blocking portion being opposed to the end surface of the first reflection mirror with a gap therebetween.