Protection device (10) for a stator of a gas turbine of the type comprising a series of sectors (12) constrained to each other by connection means, each sector (12) has at least one cavity (14) having a bottom (15), in correspondence with at least one cavity (14), a corresponding sheet (20) equipped with a series of pass-through holes (21) and suitable for covering at least one cavity (14) is fixed on an outer surface of the relative sector (12), each sector (12) is cooled by means of a stream of air coming from the pass-through holes (21) of the corresponding sheet (20) which is passed on the bottom (15) and discharged from at least one outlet hole, the bottom (15) of each sector (12) comprises a series of protuberances (30) to increase the thermal exchange surface and increase the cooling efficiency of the protection device (10).