Abstract: The invention relates to a high-pressure device (1) having a cylindrical high-pressure vessel (3) and prestressing means in order to exert an axial pressure on the vessel. The vessel (3) can have been formed from a number of layers of composite material, such as glass, carbon or aramide fibers which are oriented in the peripheral direction and are embedded in a matrix of epoxy resin or polyurethane. By applying the axial prestress to the pressure vessel (3), the tangential stress is distributed more uniformly over the wall thickness of the high-pressure vessel (3), the stress decreasing at the inside of the wall and increasing at the outside thereof. As a result, the innermost fibers of a high-pressure vessel (3) made of composite material are subjected to appreciably less stress, which has a beneficial effect on the life of the high-pressure vessel (3), and all fibers of the wall are utilized effectively.