0 3 part of divinyl benzene in a water solution composed of 400 parts of ion exchange water 1 part of hydroxypropylcellulose and 5 parts of potassium persulfate in weight and dropping the mixed solution in an atmosphere of nitrogen disperse 80 parts of magnetic powder toda corp mta 305 previously surface processed with silane coupling agent toray silicone co ltd sz6083 and 1 part of charging control agent nippon chemical industrial co ltd kaya charge t 2n in 500 parts of the emulsion and hold it while stirring at 70 u00b0 c for 3 hours in this case because of being processed above the glass transition temperature of resin components particles including polymers aggregate and aggregations average particle size of 7 u03bcm are formed after cooling add 0 5 part of silica wacker co ltd h 2000 to aggregated particles obtained by filtration water washing and vacuum drying thus producing a magnetic toner this magnetic toner indicates a specific volume resistivity of 10 15 u03c9 u00b7 cm and an amount of toriboelectric charge of 26 u03bcc g as the control obtain magnetic toner spherical particles having a composition similar to the aforesaid by a publicly known polymerization process this magnetic toner has an average particle size of 6 5 u03bcm and indicates a specific volume resistivity of 10 15 u03c9 u00b7 cm and an amount of triboelectric charge of 18 u03bcc g a magnetic developer is obtained by mixing the aforesaid magnetic toner with magnetic carriers indicating a specific volume resistivity of 10 11 u03c9 u00b7 cm prepared by surface coating heteroshaped iron powder average particle size of 25 u03bcm with silicone resin and developing is performed using a developer shown in fig5 table 7.