The present invention relates to a manufacturing method of medical sterilized normal saline, more specifically, to such a method for manufacturing sterilized normal saline for medical purpose with effective sterilizing efficacy comprising: a step of disposing at least one electrode set immersed in saline solution of pH 4.0 to pH 7.5 including a pair of electrodes with flat surface separated from each other by an interval between 1 mm and 3 mm, the flat surfaces of the electrodes facing each other; and a step of supplying 3 OmA to 20 OmA direct current to the electrodes by applying 2.4V to 3.3V DC power to the electrodes; wherein free chlorine is reliably and stably generated as having concentration range between 0.17 ppm and 6 ppm from electrolysis between electrodes.