The influence of the concentration of sodium nitrate aqueous solution electrolyte on the machining characteristics of wire electrochemical finishing using bipolar pulses was investigated. The material removal rate and surface roughness obtained remained almost the same as the concentration was varied from 0.2 wt% to 20 wt%. However, smaller surface roughness was obtained with a smaller depth of cut under a lower electrolyte concentration. Hence, the deterioration of the geometrical accuracy of the workpiece owing to the electrochemical finishing operation can be better suppressed using a lower electrolyte concentration. The measured glossiness of the finished surface obtained with a lower electrolyte concentration was higher. To understand the reason for the particular characteristics obtained from a lower electrolyte concentration, the temperature and current density distributions were analyzed. The results showed that the current density is more localized in a gap with lower electrolyte concentrations owing to Joule heating. Consequently, considering environmental issues, the use of the 0.2 wt% electrolyte is the most appropriate under the conditions adopted in the present work.