PURPOSE: To provide an ozone cleaning technology for pipeline systems for water supply and discharge wherein by the technology, scales composed of calcium-containing compounds adhering to the inner walls of a pipeline are easily removed and thick oxide film is formed within a short time.

CONSTITUTION: An ozone cleaning apparatus is provide with an ozone generating part 1, an ozone mixing part 6, and an oxidation accelerating agent injecting part 10, wherein the mixing part 6 is connected with the ozone generating part and a water supplying and discharging pipeline system and injects ozone to the supplied or discharged water and returns the water to the water supplying and discharging pipeline system and the injecting part 10 injects an ozone oxidation accelerating agent consisting of a peroxide solution to the supplied or discharged water. The apparatus injects ozone to the water supplying and discharging pipeline system and at the same time injects the ozone oxidation accelerating agent consisting of the peroxide solution to wash the inner wall of the pipeline system.