Apparatus for surface finishing of polyamide articles obtained by additive manufacturing,comprising: - a treatment chamber configured to receive at least one article and equipped with hermetic closure means; - heating means of said hermetically closed chamber for raising the internal temperature of said chamber and the temperature of the polyamide article placed therein to a prefixed operating temperature and for keeping it to said temperature over the whole operating time; - a liquid main tank for a liquid process material in fluid communication with said chamber to feed said liquid process material in said chamber once said operating temperature has reached, whereby part of said liquid process material vaporizes and the formed vapour comes into contact with the surface of said article causing softening of a surface layer thereof, whereas the remaining part of said liquid process material remains in the liquid phase at the bottom of said chamber in thermodynamic equilibrium with said vapour; - inner fan means placed in said chamber to move the vapour atmosphere formed therein, capable of being activated once said liquid process material is fed to said chamber; - a process material recovery unit comprising heat exchange means to cool the liquid process material discharged from the bottom of said chamber due to a positive pressure formed therein at the end of the contact step between the vapour and the article surface, and to condense the vapour of said process material from said chamber, and characterized by: - cooling and washing means for cooling and washing the walls of said chamber comprising a washing tank for a washing liquid and means (26, 28) for dispensing said liquid on the walls of said chamber. - a treatment chamber configured to receive at least one article and equipped with hermetic closure means; - heating means of said hermetically closed chamber for raising the internal temperature of said chamber and the temperature of the polyamide article placed therein to a prefixed operating temperature and for keeping it to said temperature over the whole operating time; - a liquid main tank for a liquid process material in fluid communication with said chamber to feed said liquid process material in said chamber once said operating temperature has reached, whereby part of said liquid process material vaporizes and the formed vapour comes into contact with the surface of said article causing softening of a surface layer thereof, whereas the remaining part of said liquid process material remains in the liquid phase at the bottom of said chamber in thermodynamic equilibrium with said vapour; - inner fan means placed in said chamber to move the vapour atmosphere formed therein, capable of being activated once said liquid process material is fed to said chamber; - a process material recovery unit comprising heat exchange means to cool the liquid process material discharged from the bottom of said chamber due to a positive pressure formed therein at the end of the contact step between the vapour and the article surface, and to condense the vapour of said process material from said chamber, - cooling and washing means for cooling and washing the walls of said chamber comprising a washing tank for a washing liquid and means (26, 28) for dispensing said liquid on the walls of said chamber.