Sterilization is essential for inactivation of microorganisms. There are many methods of sterilization, such as the use of heat or chemical processes. However, some equipment can be damaged by heat and can only be sterilized at low temperatures. Failure to properly disinfect or sterilize equipment may lead to transmission via contaminated objects. This paper presents a sterilization process using ozonized water at a temperature of 29.5°C with gram-negative bacteria (Escherichia coli). The antibacterial effect was examined with various concentrations of ORP (oxidation reduction potential) at 702 mV, 802 mV, 940 mV, 950 mV, and 960 mV. A strong linear correlation was observed between ORP value and the surface area of the antibacterial effect. It was found that increasing the concentration of ORP affects the surface area of Escherichia coli.