The invention relates to an anchor device for a prestressed diaphragm wall, comprising at least one prestressing reinforcement and a sleeve encasing said at least one prestressing reinforcement and forming an anchorage for said at least one prestressing reinforcement in the diaphragm wall, a length (Ld) of the anchor sleeve being strictly less than a length (La) of said at least one prestressing reinforcement, the anchor sleeve comprising a sealing material disposed in such a way as to coat each prestressing reinforcement, the anchor device comprising a corrosion-resistant coating of each prestressing reinforcement.