A linear illumination device of the present invention includes: a guide made of a light transmitting material extending in a first direction, having a side face and at least one end face; at least one light emitter for allowing light to enter interior of the guide from the at least one end face of the guide; and a light diffusing section formed on part of the side face of the guide, for diffusing the light incident thereon, wherein at least part of the light entering the interior of the guide goes out from part of the side face of the guide facing the light diffusing section, thereby providing substantially linear illumination light along the first direction.