Based on its molecular structure, much was expected from the results of adhesion tests of paints applied over polyamide resin (Nylon). The results were not as good as had been expected. This may be attributable to its high crystallinity. However, such a paint as wash primer, using acid catalyst, shows slightly better results. This may be due to some change in crystallization caused by partial hydrolysis of polyamide. Taking Nylon heat resistance into consideration, the surface was pretreated with phosphoric acid and adhesion tests were conducted on various types of paints. It was found that epoxy resin paint was the best and all other paints also showed good adhesion. It was found that the optimum treatment was immersion in 40 percent phosphoric acid solution at 30 degrees C for 10 minutes.