To provide a light distribution control device having the diffusive distribution symmetrical to the always constant directional axis regardless of an incident angle.

This system is composed of a light transmissive or light reflective plate or film-like structure having a large number of projecting strips juxtaposed by bring into contact in parallel with each other on at least one surface, forming a part of an almost circle out of a cross section orthogonal to the lengthwise direction of the projecting strips and being smooth in a surface of the respective projecting strips to a degree of not causing large irregular diffusion of the light. An angle of circumference and a maximum diameter of the cross section of such projecting strips are selected so that a diffraction light quantity to an incident light quantity has a sufficient rate for a use purpose in a diffraction grating effect caused by parallel contact of the projecting strips. A beam of light incident on the structure is diffused, and projection of the diffusive distribution to a surface orthogonal to both the projecting strips and a plane of the structure becomes almost symmetrical with a normal at an incident point as the axis regardless of the incident angle.