NOVELTY - The gas diffusion electrode consists of at least one catalyst layer containing supported catalyst and an unsupported catalyst layer containing catalyst, provided sequentially on a gas diffusion medium. The content of catalyst contained in the unsupported catalyst layer is higher than the catalyst contained in the catalyst layer. The gas diffusion medium is an electron conductive medium. The supported or unsupported catalyst comprises platinum, palladium, rhodium, iridium, osmium and/or ruthenium or their alloys with non-precious metals.    USE - Gas diffusion electrode is used in fuel cell (ion-exchange membrane fuel cell), oxygen-depolarized aqueous hydrochloric acid electrolyser, battery system, sensor system and membrane electrode unit (all claimed).    ADVANTAGE - The gas diffusion electrode is manufactured efficiently.    DETAILED DESCRIPTION - The gas diffusion electrode consists of at least one catalyst layer containing supported catalyst and an unsupported catalyst layer containing catalyst, provided sequentially on a gas diffusion medium. The content of catalyst contained in the unsupported catalyst layer is higher than the catalyst contained in the catalyst layer. The gas diffusion medium is an electron conductive medium which comprises carbon fiber papers, graphitized carbon fiber papers, carbon fiber fabric, graphitized carbon fiber fabric and/or sheets, which is rendered conductive by addition of carbon black. The gas diffusion electrode has 2 or 3 gas diffusion mediums. The supported or unsupported catalyst comprises platinum, palladium, rhodium, iridium, osmium and/or ruthenium or their alloys with non-precious metals such as iron, chromium, zirconium, nickel, cobalt, manganese, vanadium and/or titanium. The gas diffusion electrode comprises at least one catalyst layer on gas diffusion medium towards a membrane comprising at least one catalyst containing carbon, preferably carbon black, graphite or graphitized carbon black as support. The supported catalyst comprises platinum, palladium, rhodium, iridium, osmium and/or ruthenium metals as catalyst. The supported catalyst further comprises gold and/or silver. The supported catalyst is an alloy of platinum, palladium, rhodium, iridium, osmium and/or ruthenium or iron, cobalt, nickel, chromium, manganese, zirconium, titanium, gallium and/or vanadium. The unsupported catalyst comprises black precious metal catalysts such as platinum, palladium, rhodium, iridium, osmium and/or ruthenium, or alloy of platinum, palladium, rhodium, iridium, osmium and/or ruthenium or iron, cobalt, nickel, chromium, manganese, zirconium, titanium, gallium and/or vanadium, preferably platinum or platinum-ruthenium metal catalysts. The supported catalyst layer is platinum black or platinum-ruthenium black.