To provide a purification method for the contaminated ground which curtails a treatment time and reduce a treatment cost by efficiently sucking/removing liquid state contaminants existing in soil located to be equal to or below the level of groundwater and high concentration contaminated groundwater around the soil.

The method includes a purification body installation process for installing an underground freezing pipe and a first underground suction body at an appropriate pitch in the contaminated ground in which the contaminants exist in the soil located to be equal to or below the level of the ground water, a freezing process for freezing a contaminated ground region, and a liquid suction process for sucking the liquid state contaminants from the first underground suction body while a frozen state is maintained.