A method is provided for producing a joint member of a metal joint, such that reduction of assembly manhours and reduction of the thickness and weight can be achieved at the same time without reducing the strength of a product or increasing the cost of production. In the case of a nut-side thin joint member, a metal plate of boron steel obtained by adding boron to low-carbon steel is burred such that the resulting cylindrical body obtains a surface that is sufficient for threading, then a threaded portion having a plurality of threads is formed on that surface, after which, quenching is carried out to increase the strength of the threads so that a nut having sufficient strength can be integrally provided even though the thickness and weight of the joint member are reduced.