From the standpoint of the complex-forming capacity of nitrogen that fixes the plating catalyst, a high pH is preferable; however, since the stability of the solution drops in the case of a high pH, a pH in the range of 1.5 to 7 is desirable. [0024] In regard to the method used to treat the article of plating with the pretreatment agent, methods such as immersion, coating with a brush, spin-coatin