Laser lights emitted from a light source 30 are diffused in a direction parallel to main surfaces of a light guide plate 9 by a one-dimensional diffuser 5. The diffused laser lights are converted to parallel lights by a first cylindrical lens 6, and are then converged in a direction of the thickness of the light guide plate 9 by a second cylindrical lens 7. The converged laser lights are reflected 90 degrees twice by a mirror 8, and are guided to a side surface of the light guide plate 9.