To provide a draining method which does not cause a factor responsible for degradation of working efficiency.

The draining method is employed when underground walls 12 are constructed so as to be opposite to each other under the ground 10 and the ground inside the underground walls 12 is excavated while the groundwater level being lowered. The underground wall 12 is formed by excavating an excavated groove 14 in the ground, building a cage in the excavated groove 14, and placing concrete therein. At this time, a draining means 16 is embedded in the underground wall 12, which lowers the underground water level. The embedded draining means 16 includes water collecting sections 18, drainage pipes 20, and a suction pump. The water collecting sections 18 are arranged at respective internal lower ends of the underground wall 12, along an extending direction of the wall 12 at predetermined intervals. The drainage pipes 20 are erected in the vertical direction of the underground wall 12. Each pipe 20 has its lower end communicate with the water collecting section 18 and has its upper end extend up to the ground, and the upper end of each pipe 20 is connected to the suction pump and communicates with the same on the ground.