Abstract: A coffee machine comprises a boiling chamber, two pistons adjustable independently of each other and adapted to be pushed into the boiling chamber from opposite sides and defining between them a boiling space to hold and boil a predetermined quantity of powdered coffee, a source of boiling water having a through-flow heater and a boiling water pressure generator, and a hydraulic actuating device for the pistons having a pressurized medium circuit including a pressurized medium pump. The boiling water pressure generator is constituted by a media converter, of which one side is incorporated into the water supply to the boiling chamber while its other side is connectible to the pressurized medium pump.