To provide repair wall construction of the existing underground structure, capable of completely waterproofing a wall in a basement or the like of the existing building, and at the same time, improving its earthquake resistance.

Repair wall construction of the existing underground structure is so constituted, that it can promote earthquake resistance by preventing the water leakage of the existing wall in a basement or the like, and at the same time, by executing reinforcement in terms of strength. Execution of work is so carried out that a waterproofing membrane 3 formed by applying a bentonite 3b to a resin membrane 3a is stuck on a wall surface W, and that a reinforcing plate (steel plate) 1 is fixed to the surface side in a state of a specific interval with a plurality of mounting bolts 2. Shrinkage-compensating mortar is poured into a gap G, where a partition is formed between the waterproofing membrane 3 and the reinforcing plate 1 to form a mortar layer 4. By the constitution, the waterproofing membrane 3, mortar layer 4 and reinforcing plate 1 are integrally connected to each other to construct a strong repair wall. Since the repair wall is fixed to the existing wall with the mounting bolts 2, the repair wall is completely waterproofed, and at the same time, it is reinforced to promote earthquake resistance in terms of strength.