of magnetic powder can be included in the resin it is desirable that the relative surface area the magnetic powder is within the range of 1 0 u02dc 7 0 m 2 g on the other hand the magnetic powder adhered to the surface of the carrier particles having magnetic powder dispersed in resin has a large relative surface area preferably within a range of 8 0 u02dc 12 0 m 2 g and more preferably within a range of 8 0 u02dc 10 0 m 2 g to suppress the amount of exposure of the magnetic powder on the surface of the carrier particles and achieve a suitable carrier resistance value the content of magnetic particles having a small relative surface area is desirably 60 u02dc 90 percent by weight and preferably 80 u02dc 90 percent by weight relative to the resin particles containing dispersed magnetic powder when the aforesaid magnetic powder content is less than 60 percent by weight the obtained carrier has a weak magnetic force such that during development the carrier adheres to the image bearing member and produces noise in the formed image and the image bearing member is damaged by the adhered carrier when the aforesaid magnetic powder content exceeds 90 percent by weight it becomes difficult to accomplish the kneading necessary to uniformly disperse the magnetic powder in the resin the content of magnetic particles having a large relative surface area adhered to the surface of the carrier particles cannot be discussed unconditionally due to variations of the carrier particle size amount of magnetic powder contained in.