The catalytic activity for methylation of benzene was found on Co/MFI zeolite; the activity was generated by loading of Co in the region of Co/Al molar ratio in the final solid=0.2-0.6 (significantly increased at 0.3-0.4) on a support MFI with [Al]=1.3molkg(-1). It has been found that the low activity at Co/Al>0.6 was ascribed to the cobalt oxide aggregate formation, but even in the region of Co/Al<0.6 where cobalt was mono-atomically dispersed, the presence of at least two types of cobalt species, active and inactive ones formed at Co/Al>0.2 and Co/Al<0.2, respectively, is suggested. Even in the low Co/Al region, addition of typical divalent elements such as Mg, Zn, Pb and Ca during the Co loading process was found to generate the catalytic activity. It is speculated that the active cobalt species were selectively formed. [GRAPHICS]