A method for producing an oxygen-containing compound comprising: an ozonization reaction step continuously supplying, together with an organic compound being a terminal olefin, a cyclic olefin, or an internal olefin, ozone having an oxygen content of less than 10% in a dissolved state in high-pressure carbon dioxide having a pressure within 3 to 30 MPa to an ozonization reaction section having a thin tubular shape formed of a thin tube having a tube diameter of 1.0 mm to 30 mm that may include a curved shape, and reacting the ozone and the organic compound under following condition(s) that suppresses generation of oxygen due to thermal decomposition of the ozone, thereby continuously producing an ozonide, wherein any one of following conditions (a) or (b) or both are met, (a) a flowing rate of a fluid containing the ozone, the organic compound, and the high-pressure carbon dioxide supplied to the ozonization reaction section is adjusted to a range from 0.5 mL/min to 10.0 mL/min, (b) a concentration of the ozone in the ozonization reaction section is adjusted to a range from 0.01 M to 0.5 M; and a decomposition reaction step provided in a manner continuous with the ozonization reaction step, the decomposition reaction step continuously supplying the ozonide produced in the ozonization reaction step to a decomposition reaction section having a thin tubular shape formed of a thin tube having a tube diameter of 1.0 mm to 30 mm that may include a curved shape, thereby continuously producing an oxygen-containing compound. an ozonization reaction step continuously supplying, together with an organic compound being a terminal olefin, a cyclic olefin, or an internal olefin, ozone having an oxygen content of less than 10% in a dissolved state in high-pressure carbon dioxide having a pressure within 3 to 30 MPa to an ozonization reaction section having a thin tubular shape formed of a thin tube having a tube diameter of 1.0 mm to 30 mm that may include a curved shape, and reacting the ozone and the organic compound under following condition(s) that suppresses generation of oxygen due to thermal decomposition of the ozone, thereby continuously producing an ozonide, wherein any one of following conditions (a) or (b) or both are met, (a) a flowing rate of a fluid containing the ozone, the organic compound, and the high-pressure carbon dioxide supplied to the ozonization reaction section is adjusted to a range from 0.5 mL/min to 10.0 mL/min, (b) a concentration of the ozone in the ozonization reaction section is adjusted to a range from 0.01 M to 0.5 M; and (a) a flowing rate of a fluid containing the ozone, the organic compound, and the high-pressure carbon dioxide supplied to the ozonization reaction section is adjusted to a range from 0.5 mL/min to 10.0 mL/min, (b) a concentration of the ozone in the ozonization reaction section is adjusted to a range from 0.01 M to 0.5 M; and a decomposition reaction step provided in a manner continuous with the ozonization reaction step, the decomposition reaction step continuously supplying the ozonide produced in the ozonization reaction step to a decomposition reaction section having a thin tubular shape formed of a thin tube having a tube diameter of 1.0 mm to 30 mm that may include a curved shape, thereby continuously producing an oxygen-containing compound.