A measurement system that couples a commercial microcalorimeter with usual electrochemical instruments was established for electrochemical calorimetry of electrode reactions. Apparent enthalpy change of anodic oxidation of ferrocyanide ion to ferricyanide ion and apparent enthalpy change of cathodic reduction of hydrogen ion to hydrogen gas were determined with this system. The difference between the apparent enthalpy change and the value calculated with conventional thermodynamic data of aqueous ions was found to be a constant at a given temperature. This system can further be used to determine unknown standard enthalpy changes of electrode reactions.