To smoothly and efficiently return water in the ground without clogging the ground by an oxide granular material of dissolved iron in returning the pumped-up water.

This method pumps up underground water flowing inside a pumping casing pipe 2 buried in the ground 1, and returns the pumped-up underground water again underground via a return casing pipe 3 buried in the ground 1. A series of pumping water return passage 4 is formed for returning the water in the ground 1 by pressurization via the return casing pipe 3 by pumping-up the underground water flowing inside the pumping casing pipe 2. This series of pumping water return passage 4 is formed as a sealed passage cut off from the atmosphere to prevent the water from touching the atmosphere before returning in the ground 1 via the return casing pipe 3 by pumping up the underground water from the pumping casing pipe 2.