A first joining object and a second joining object are joined to each other using an insert material. The first joining object and/or the second joining object has a first metal composed of Sn or an alloy containing Sn. The insert material contains, as a main component, a second metal which is an alloy containing at least one selected from among Ni, Mn, Al and Cr, and Cu, and is located between the first joining object and the second joining object. When subjected to heat treatment to produce an intermetallic compound of the first metal and the second metal, the first joining object and the second joining object are joined to each other.