To provide a lighting device which can be surely and easily mounted on a suspension bolt by a simple structure.

The lighting device comprises a lighting device body 1 assembled into a square shape by lateral frame members 9 and vertical frame members 10, a pair of mounting plates 7 in which, a mounting hole 7a for the suspension bolt is formed, movably mounted on the bottom of the lighting device body leaving a space between them, and a guiding means G guiding respective mounting plates. The guiding means is composed of a supporting step 10c1 at the bottom and a guiding part 7b arranged at both ends of the mounting plate, and the supporting step 10c1 having a slide groove is formed with a positional relation that faces the opening edge of a back surface side opening 1b of the lighting device body, and the guiding part 7b is inserted into the slide groove.