Sb$_2$S$_3$ thin films have been obtained by physical vapour deposition on LiNbO$_3$ and glass substrates. Films with amorphous structure originally became polycrystalline by annealing in a sulfur atmosphere. Changes in optical and structural properties have been studied as a function of annealing temperature. A drastic variation in optical transmission, energy gaps, refractive index, crystallite size, etc is observed at a temperature near 200 $^∘$C.