The invention relates to a testing device for fuselage shells, wherein the test piece is connected to a complementary cross-sectionally U-shaped structure with legs, wherein longitudinal flanges are provided at the ends of the legs in the longitudinal direction of the complementary structure, with means for fixing the fuselage shells to the complementary structure and also for introducing and receiving corrective forces, and transverse flanges are provided at the limitations of the complementary structure in the longitudinal direction, for introducing and receiving testing forces in six degrees of freedom. The complementary structure (1) is formed as a soft box of composite materials and the U-shaped cross section of the complementary structure (1) is made up of a horizontal straight portion (11) and two respectively laterally adjoining ellipsoidal portions (12), which form the legs (3) of the U-shaped complementary structure (1).