[Problem] There is provided a method for producing an oxygen-containing compound safely and with improved reaction efficiency, in which an undesired peroxide is unlikely to be produced, and efficient heat exchange of the ozonization can be achieved.[Mean for solving the Problem] The method comprises an ozonization reaction step of continuously supplying, together with an organic compound, ozone having an oxygen content of less than 10% in a dissolved state in high-pressure carbon dioxide to an ozonization reaction section having a thin tubular shape, and reacting the ozone and the organic compound under conditions that suppress generation of oxygen due to thermal decomposition of the ozone, thereby continuously producing an ozonide; and a decomposition reaction step of continuously supplying the ozonide produced in the ozonization reaction step to a decomposition reaction section having a thin tubular shape, thereby continuously producing an oxygen-containing compound, the decomposition reaction step being provided in a manner continuous with the ozonization reaction step.