Abstract: According to the present invention, a resin molded product provided with engaging projections to be engaged with engaging members, which have been previously formed in side walls of a frame member, and wing members to be in contact with top portions of the side walls of the frame member alternately formed on the side walls thereof is used as a rod lens of the linear light source. Thus, a curvature of the rod lens can be optionally selected and the linear light source is superior also in assembling. In addition, in the case where this rod lens is composed of a lens surface covering a width of opening of the frame member and an almost flat counter surface positioned opposite to this lens surface, a light-scattering effect is brought about in the counter surface of the rod lens by taking a refractive index or a thickness of this rod lens into consideration, whereby a width of illumination can be increased.