To improve the ease and stability of assembly and reduce irregular emission from light emitting surfaces when combining a plurality of lighting systems 1 for lighting.

The rectangular parallelepiped lighting system includes a casing 2 formed in an approximately rectangular parallelepiped shape with an opening portion 2A on one face, a light guide lens 3 provided in the opening portion 2A and formed in a rectangular shape, a light source 4 provided in the casing 2 for emitting light toward the light guide lens 3, and a position adjusting mechanism 5 having a grip portion 54 on the outside of the casing 2 for adjusting the position of the light source 4 with the operation of the grip portion 54.