To enhance production efficiency and the reduction of an assembling error of a part by simplifying work when a constitution part of a lighting system is assembled to a base member.

The vehicle interior lighting system is provided with the base member 22 of the lighting system 20; a printed board 24 having a light source (bulb 24a) for illumination and switches and assembled to the inside of the base member 22; a mounting member (bezel 26) for fixing the board to the base member 22; and a lens 28 for illumination fixed to a surface side in a state that the lens covers the inside of the base member. The printed board, the mounting member and the lens are assembled to the base member, respectively, so as to be superposed from either of front and back sides.