A direct bonding method of metal and resin comprises a first step where the metal material is subjected to electrolytic treatment by using a carboxylic acid to form a new surface, which is then coated with the carboxylic acid to obtain a carboxylic acid-coated metal material; a second step where the resin material and the carboxylic acid-coated metal material are laminated to form an interface to be bonded; a third step where the interface is heated to Tg of the resin material or higher by heating means to remove water from the interface, the decomposition of the resin material generates a carboxyl group, and the new surface is exposed on the surface of the carboxylic acid-coated metal material by removal of the carboxylic acid; and a fourth step where the interface is cooled below the Tg to form a bonded part by bonding the carboxyl group and the new surface.