In this study, high-purity silver nanocolloids were synthesized by an electrolytic reaction, and the effect of temperature on the nanocolloid concentration was analyzed by performing the reaction at 70 °C and 90 °C. The antibacterial properties of the thus-synthesized silver nanocolloids were also studied. When the synthesis was performed at 90 °C, the concentration of silver nanocolloid increased to 14 mg/L after 5 min, 1756 mg/L after 30 min, and 2147 mg/L after 60 min. The concentration of silver nanocolloid synthesized by electrolytic reaction at 70 °C and 90 °C for 60 min was 1,882 mg/L and 2147 mg/L, respectively. The preferred temperature at which the electrolytic synthesis is performed is 70 °C to obtain high concentrations of 1,000 mg/L or more. The antibacterial performance of the thus-synthesized silver nanocolloids was 99.9% for E. coli and 99.5% for Pseudomonas aeruginosa.