Joining method of metal

Between the first substrate portion 12 first coating portion 14 and the second coating portion 24 covering the (copper oxide) and the second substrate portion 22 (copper) (copper oxide) covering the (copper) in a solution 30 which copper oxide copper oxide and a second coating portion 24 of the first coating unit 14 is eluted filled, the copper oxide constituting the first coating portion 14 and the second coating portion 24 solution It is eluted in 30. As the pressure of the solution 30 is increased, while pressing the first bonding portion 10 with a press machine and the second bonding portion 20, it is heated at a relatively low temperature conditions of 200 ° C. to 300 ° C. it by removing the components other than copper in the solution 30 to precipitate the copper, are bonded by copper deposited the first base member 12 and the second base material 22.