The liberalization movement in Japan will be expanded to the residential sector and full liberalization of the retail market will be achieved in near future. Under this background, it is expected that transaction in Distribution Network (DN) which has many consumers of the residential sector is activate. Furthermore, consumers can control their loads depending on selling prices offered by retailers with introducing Demand Response (DR) technology such as Home Energy Management System (HEMS). Due to the variation of load by DR, however, a voltage profile in DN could be changed compared to the present situation. This may make the voltage management difficult and cause several problems such as voltage deviation from an adequate range. In this paper, the impact of DR in a liberalized electricity market on DN is evaluated for efficient voltage management. In order to evaluate the behavior of the retailer and consumers, this paper proposes a bi-level programming approach based on the Stackelberg game model. Solving the bi-level programming problem including the power flow equation for a DN model based on IEEE 13-bus test feeder, we analyze the impact of retailer and consumers on voltage in DN in order to account for transaction between these market players.