To provide a ground water lowering method capable of directly discharging ground water from the inside of the ground to artesian aquifer without pumping up on the ground, and a ground water lowering device therefor.

This ground water lowering method comprises constructing a water injection well 3 in the periphery of an excavating position, injecting ground water D in the ground C to the water injection well 3, pushing down the ground water D by a ground water press-in mechanism provided within the water injection well 3, and discharging the ground water to the artesian aquifer 5 located under a water impermeable layer 4, whereby a level A located above an excavation floor surface 1 is lowered to a level B located under the excavation floor surface 1. The operating state of the water injection well 3 is observed by an observation well 2 for observing the ground water level.