A joint structure includes a first conductor and a second conductor, and a laminated bonding material that is arranged between the first conductor and the second conductor to bond the first conductor to the second conductor. The laminated bonding material includes a first bonding material layer bonded to the first conductor, a second bonding material layer bonded to the second conductor, and an auxiliary conductor plate arranged between the first bonding material layer and the second bonding material layer. The auxiliary conductor plate has a melting point higher than melting points of the first bonding material layer and the second bonding material layer. The second conductor has a laser irradiation mark on a back surface thereof, the back surface being opposite to a front surface of the second conductor that faces the laminated bonding material.