The present invention can give a joining structure using metal nanoparticles to join the same types or different types of metal where when one surface metal is Al based, the parts are joined through a joining layer containing Ni nanoparticles, whereby a good joining strength is obtained. Further, by using two joining layers (6, 8) including metal nanoparticles to sandwich metal foil (7) so as to form a joining layer and joining the same type or different types of surface metals (3-4) through this joining layer, it is possible to ease the thermal stress due to the difference in amounts of thermal expansion of joined members which have two surface metals.