To provide a method of cleaning a contaminated ground by which contaminants in the ground is sufficiently allowed to react with ozone in a cleaning gas and the contaminants are sufficiently recovered by pumping-up a compound produced by the reaction together with the under ground water to the ground regardless of an unsaturated zone or a saturated zone.

A plurality of lifting pipes 3 are penetrated into the ground around the contaminated zone of the contaminated ground. The level of the under ground water in the contaminated zone is lowered by pumping-up the under ground water to the ground through the lifting pipe 3. As the level of the under ground water is lowered, the cleaning gas containing ozone as a composition gas is supplied to the under ground through the plurality of the cleaning pipes 13. Next, the pumping-up of the under ground by the plurality of the lifting pipes 3 is stopped to raise the level of the under ground water. After the water level is raised to the initial level, the ground water is pumped up again to the ground through the lifting pipes 3. After the under ground water is pumped-up, the steps are successively repeated from the step of supplying the cleaning gas depending on the progress of the cleaning by the cleaning gas in the under ground of the contaminated zone.