A two-component developing agent retained on the periphery surface of a magnetic roller 11 and a development roller 12 are brought in contact with each other, the nonmagnetic toner in the two-component developing agent is electrostatically adhered to the periphery surface of the development roller 12, and the nonmagnetic toner on the development roller 12 is sprayed on the periphery surface of a photosensitive drum 13, thereby causing an image of an electrostatic latent image to appear on the photosensitive drum 13 as a toner image. The two-component developing agent for an image forming device thus configured comprises a nonmagnetic toner comprising color particles, and a magnetic carrier, wherein the magnetic carrier has a resin coating layer on the magnetic particle surface, and the critical surface tension of this resin coating layer is 25 dyn/cm or less.