PURPOSE: To easily carry out fitting operation in an actual site from a tower body 1 side in safety without fitting illuminators, one by one, in separate process.

CONSTITUTION: A lattice-shaped frame body 3 which is framed in a lattice shape and has many lattice frames 2 formed on its front surface is provided integrally to the tower body 1, and a screen box unit 8 consisting of a light- transmissive sheet 5 having a screen part 4 as its front surface, a casing 6 formed by extending the sheet 5 at an opening part 6a, and an illuminator 7 installed in the casing 6 is fitted in each lattice frame 2 of the lattice-shaped frame body 3 detachably from the side of the tower body 1 so that screen parts 4 provided to respective box units 8 are successive.