PURPOSE: A method for preparing subcritical water extract of onion skin using purified water is provided to obtain an antibacterial agent. CONSTITUTION: A method for preparing subcritical water extract of onion skin comprises: a step of mixing washed onion skin and diatomaceous earth in a ratio of 1:2-1:3 to prepare a sample； a step of adding the sample to 34ml or 66ml of a cells； a step of adding distilled water； and a step of extracting at 60 pressure and 100 degrees Celsius for 15 minutes. An antibacterial agent contains the subcritical water extract of onion skin.본 발명은 농산 부산물로서 폐기되는 양파껍질을 정제수를 추출용매로 하는 아임계 수추출방법을 제공하며 상기 방법에 의하여 제조된 양파껍질의 아임계 수추출물을 유효성분으로 하는 항균제를 제공하는 뛰어난 효과가 있다.
