Abstract: An exoskeleton (1) for supporting a user's arm, comprising a supporting frame (2) that supports an up-and-down movable standard (3, 3?) on which a horizontally movable arm (4, 4?) is mounted. On an extremity of the horizontally movable arm (4, 4?) a back support (5, 5?) is mounted and a supporting arm construction (6, 6?) for supporting the user's arm. The supporting arm construction (6, 6?) is articulated and extendable so as to tailor the arm construction (6, 6?) to the user's arm dimensions. Further, the supporting arm construction (6, 6?) has two limbs (7, 8; 7?, 8?) that connect to each other with a hinge (9, 9?). On opposite sides of the hinge (9. 9?), the limb (8, 8?) that is farthest away from the back support (5, 5?) connects to counterbalancing springs (10, 11; 10?, 11?) that on their opposite sides connect to the upper limb (7, 7?) and directly or indirectly to the horizontally movable arm (4, 4?).