A sterilization method is provided which acquires microbicidal activity equivalent to plasma-treated solution or more powerful than the same without the use of a plasma generation device. The sterilization method includes applying liquid containing peroxynitric acid (HOONO2) produced by chemical reaction to an object to be sterilized under acidic conditions of a pH value of 4.8 or lower. The liquid containing the peroxynitric acid is produced by mixing nitrous acid and peroxide together, for example, mixing nitrite and peroxide together.
