An environmentally friendly electrochemical protocol about cobalt-catalyzed C-H amination of arenes has been developed, which offers a simple way to access synthetically useful arylamines. In divided cells, a wide variety of arenes and alkylamines are examined to afford C-N formation products without using external oxidants, which avoids the formation of undesired byproducts and exhibits high atom economy. Importantly, the reaction can also be extended to gram level with moderate efficiency. KIE experiments indicate that C-H bond cleavage might not be involved during the rate-limiting step.