Synthesis of disulfide polymer by electrochemical polymerization of 1,10-decanedithiol (DEDT) in acetonitrile (CH3CN) was investigated. Pt electrode and Bu4NClO4 as supporting electrolyte were found to be suitable for the electrochemical polymerization of DEDT. The polymerization of DEDT proceeded to give polymer in good yields, and the obtained polymers were found to be a linear disulfide polymer. The polymer yield was proportion to current quantum, but Mn of the polymer did not depend on both monomer concentration and current quantum. The polymer yield increased by the addition of dibenzyldisulfide (DBDS).