Disclosed is a carrier core material containing at least one metal oxide (M L O) having a melting point of not higher than 1000°C and at least one metal oxide (M H O) having a melting point of not lower than 1800°C, wherein the metal (M H ) for constituting the metal oxide (M H O) has an electrical resistivity of not less than 10 -5 ©·cm. Also disclosed is a two-component developing agent comprising a coated carrier, which comprises the carrier core material coated with a resin, and toner particles. Further disclosed is an image forming method comprising developing an electrostatic latent image formed on a photosensitive member with the two-component developing agent using an alternating electric field. The carrier core material and the coated carrier have high magnetization and are free from occurrence of leakage of electric charge over a wide range of electric field from low electric field to high electric field. According to the two-component developing agent of the invention, an excellent image can be formed.