Brazing of Al to Cu using Al-Si-Mg-Bi brazing alloy has been carried out in a vacuum furnace. In the brazed interlayer, there were two kinds of intermetallic compounds. One of these intermetallic compounds was θ phase and the other was δ(Cu3Al2). Tensile strength of the joint was only about 15MPa. Deformation behavior of Al/Cu brazing joint was brittle without deformation of the base metal. The specimen was fractured in the intermetallic compound which was mainly θ phase. In order to improve the tensile strength of Al/Cu dissimilar joint, Cu cladding Ag (thickness: 0.1mm) substituted for Cu. As the result, tensile strength of the joint was about 70MPa and the specimen was fractured in an Al base metal. In this joint, plate-like intermetallic compound, δ (Ag2Al) was formed in the brazed interlayer. The shape of δ(Ag2Al) was quite different from θ phase found in Al/Cu joint. It was considered that the shape of reaction layer remarkably affected to the strength of the Al/Ag-Cu clad dissimilar joint.