A device for filling an ink cartridge, particularly a refilling device for filling ink cartridges of ink-jet systems, such as printers and plotters, or other automatic registering, writing or drawing apparatus, includes a refilling container and an ink cartridge connected through an adaptor and arranged essentially one above the other in the filling position. The adaptor has at least two connections for the refilling container and the cartridge to be connected. A separate ink reservoir is arranged in the ink cartridge, wherein the ink reservoir of the ink cartridge and/or the filling container of the refilling container includes an easily deformable bag, and wherein the reservoir bag and/or container bag are of a flexible, elastic material. A hermetically sealed cartridge space is formed between the cartridge housing and the separate ink reservoir. The adaptor is constructed and dimensioned in such a way, that, together with the ink cartridge and the refilling container, the adaptor forms in the filling position a hermetically closed filling system and an additional air system between the hermetically sealed cartridge space and the atmosphere.