of a roller form charging member the volume resistivity of the base layer was 3 u00d7 10 4 ohm cm when measured at a temperature of 20 u00b0 c and a humidity of 50 according to jis k6911 separately 6 2 parts of poly oxypropylene triol hydroxyl value 114 5 mg koh g average molecular weight 1500 and 0 02 part of dibutyltin dilaurate were dissolved in 80 parts of methyl ethyl ketone and to the resultant solution 5 5 parts of blocked ketoxime compound available nco group content 11 6 wt predominantly comprising hexamethylene diisocyanate was further added thereby to prepare a coating material having an nco oh mol ratio i e mol of nco group mol of oh group of 1 2 the thus obtained coating liquid was applied onto the above mentioned base layer by dip coating and dried and hardened under heating at 120 u00b0 c for 60 min to form a surface layer of charging member having a thickness of 200 microns whereby a charging member was prepared separately a surface layer was formed on an aluminum sheet in the same manner as described above and its volume resistivity was measured the thus prepared charging member was assembled in an electrophotographic copying machine using a normal development system trade name pc 20 mfd by canon k k so as to provide a system arrangement as shown in fig2 the charging member according to the present invention was assembled in the copying machine instead.