In order to clarify the fundamental bending-deformation characteristics and the load property of clad tubes, the flattening behavior, the springback and the bending moment of adhesive-bonded two-layer clad tubes are investigated experimentally. The experiments were carried out on clad tubes consisting of soft aluminum, hard aluminum and copper by means of a 4-point bending test, a new measuring instrument having been developed for the continuous measurement of the flattening and the bending curvature during deformation. A unique negative flattening deformation behavior in the bending direction was observed in the case of the clad tubes (A1/A1) with hard aluminum on the outside. It is found that the springback on the bending curvature and the bending moment of a clad tube having a material with large flow stress on the outside are greater than those of a clad tube having the reverse configuration.