A stand-up wheelchair with a chassis, at which two drive wheels and at least a one guidable wheel is fastened, on which a stand-up unit with a seating surface, a backrest and at least one tiltable footrest is arranged, whereby reciprocally underneath the seating surface an upper longitudinal rail and a lower longitudinal rail are arranged, the upper longitudinal rail is firmly connected with the seating surface and both longitudinal rails are connected over four hinge points with their rear ends connected with a backrest, characterized by the fact that the rear ends of the longitudinal rails show a slot, in which the backrest can be longitudinally adjusted with their lower ends.