The present invention relates to a device for plasma-treating hollow bodies, such as bottles, vials, syringes, shut-off caps, etc., in particular with a view to sterilising said hollow bodies, and is equally suitable for various discharge types such as dielectric barrier discharge and discharges with high frequency and microwave excitation. The device allows a pressure gradient to be set between the interior and the exterior of the object to be treated, which can be advantageously used for process control and plasma formation and forms the basis for an optimised in-line method of plasma-treatment of hollow bodies. An essential feature of the invention is the original combination of a plasma process and a sealing system. According to the main claim, this is achieved with external tubes (4, 6), which are connected to each other so as to be impermeable to gas, but galvanically insulated, and of which at least one is electrically conductive, such that the external tubes form an antechamber between the two external tubes (4, 6) and a treatment chamber between the external tube (6) and the internal tube (1). Thus materialises a double-chamber system.