Electrochemical carbonylation of methanol to dimethyl carbonate (DMC) was studied over Pd/C anode with XBr electrolyte (X=Li+, Na+, Bu4N+). The formation rate, the current efficiency, and the selectivity of DMC with LiBr electrolyte were considerably higher than that with other supporting electrolyte, LiClO4, NaClO4, LiCl, Bu4NCl, LiI, and Bu4NI. A turnover number of Pd electrocatalyst for DMC formation was over 600 h(-1). Current efficiency of 80% and selectivity based on CH3OH and CO of 95% were observed. Data of kinetic experiments and stoichiometric experiments strongly suggested that electrochemically produced Br-2 works as an oxidant for the oxidative carbonylation of methanol to DMC catalyzed by Pd-0 on carbon. A very active and selective carbonylation of methanol to DMC was performed by indirect electrolysis with Br-2/Br-redox mediator.