For the investigation of fracture criteria, adhesive tensile strengths of scarf and butt joints bonded by a brittle and two ductile epoxy adhesives have been measure, and three-dimensional finite element analyses have been performed. Deformation of the Joints was influenced considerably by mechanical properties of adhesives. Fracture of the joints bonded by the brittle adhesive satisfied maximum principal stress criterion. At the scarf angles of 15° to 60°, fracture of the joints bonded by the ductile adhesives satisfied the von Mises criterion and at the scarf angles of more than 60°, a brittle (cleavage) fracture occurred in those joints by plastic constraint due to an increase of stress triaxiality in adhesive layer. Locations of fracture initiation and fracture modes of adhesive layers observed with an optical microscope and scanning electron microscope agreed with those expected from experimental results of deformation and adhesive tensile strength, and result of stress analyses.