Underground retaining wall for public works and method for constructing the same

An underground retaining wall for public works is provided to improve economical efficiency and constructability on follow-up work by using the limited land effectively and excluding the use of a strut in an excavation area, not to invade the neighboring area, to minimize the damage caused by excavation by minimizing ground subsidence and displacement and to maximize the possible depth for excavation. An underground retaining wall(10) for public works comprises a first pile row formed by installing many piles(22) continuously around an excavation area at regular intervals, a second pile row formed by installing many piles(32) continuously around an excavation area at regular intervals, and a first connection member(40) connecting and fixing the first pile row and the second pile row on the ground and including a first wale(42) coupled parallel to the piles of the first pile row, a second wale(44) coupled parallel to the piles of the second pile row and a fixing bar(46) coupled to the first wale and the second wale, wherein the first wale, the second wale and the fixing bar are coupled with one another by welding or bolting and fixed to each pile of the first and second pile rows by using a bracket(48).