The present invention relates to a preparation for sterilizing or disinfecting a tissue which has an excellent tissue sterilizing or disinfecting ability and is suitable for therapeutic or prophylactic treatment of various diseases caused by a microorganism such as a bacterium or a virus and a method for sterilizing or disinfecting a tissue. The present invention relates to a preparation for sterilizing or disinfecting a tissue and an agent for therapeutic or prophylactic treatment of a periodontal disease, characterized by containing a gas in a nanobubble state. Furthermore, the present invention relates to the above-mentioned preparation for sterilizing or disinfecting a tissue, characterized in that the above-mentioned gas in a nanobubble state is ozone. Furthermore, the present invention relates to a liquid preparation for sterilizing or disinfecting a tissue, characterized by comprising ozone-nanobubble water.