An adsorption dryer includes a pressure vessel containing the drying agent in a cylindrical chamber, which is in the form of a cylindrical tubing section. The pressure vessel is axially clamped between a bottom and a top distributor plate. In the cylindrical chamber of the pressure vessel, the drying agent is enclosed between a bottom piston and a top piston. The two pistons are radically sealed against the inside of the wall of the pressure vessel. Tongue and groove connections between the wall of the pressure vessel and the piston can hold the pistons axially. The bottom and top distributor plates are clamped with the pistons by means of threaded bolts. The tongue and groove connection between the piston and the pressure vessel and the bolt connection of the distributor plates with the pistons ensure comparatively low cost of production and assembly.