An electric junction box having a casing and a circuit structure accommodated in the casing. The circuit structure includes a plurality of first bus bars arranged at intervals and synthetic resin members disposed between the adjacent first bus bars and firmly attached to the first bus bars. The synthetic resin members have heat conductivity higher than that of air. Since the heat generated from the first bus bars during electrical connecting can be transmitted to the synthetic resin members, the electric junction box can be prevented from being locally heated to a high temperature.