A beverage carbonator device comprising an outer main container for holding the beverage as it is being, and after it is, carbonated, which is open at its upper end and has a beverage dispensing off-on control valve or spigot at its lower end, and a carbonation generating and pressure regulating assembly arranged for mounting within the container in sealed application to the container open end. The assembly includes a lower carbonating gas generating tank that is to receive and contain the carbonating gas generating substances, which tank is removably connected in sealed relation to an orificed floor of a carbonating gas receiver that is closed at its upper end by a flexible diaphragm, with the receiver in turn being secured to a cover that is part of the assembly and that is sealingly applied to the container upper end. The diaphragm is exposed to a vented breathing chamber it defines with the cover, and the diaphragm is spring biased inwardly of the receiver and carries a link that is operatively connected to a control valve for the receiver floor orifice for controlling the pressure of the carbonating gas in the container that is supplied thereto from a gas emitting conduit connected to the receiver for that purpose, to maintain the carbonating gas in the container at a substantially uniform predetermined level.