To provide a construction method in which a circular vertical shaft having a spiral passage is installed near an underground structure, and in which a connecting passage to the ground is constructed by slightly extending an earth retaining wall, and which dispenses with back-filling work, in order to overcome problems such that construction costs are increased due to the further extension of a ramp and the need to backfill a void in a part above the ramp with soil, etc., when an installation position of the underground structure is made deep, in the case of a conventional connecting passage composed of the ramp, and such that the costs are increased due to the need for excavation of an extensive area, hard work for the excavation and the need for back-filling similar to that in the above case, in the case of a circular earth retaining method.

The construction method for the connecting passage between the ground and the underground structure is characterized as follows: a plurality of discrete caissons, in which an outer shape, composed of internal and external walls and both side walls, and the inside of the outer shape are divided by a inclined slab, are sunk in the ground in such a manner that all the caissons are adjacent to one another; after that, the opposed side walls of the adjacent caissons are removed; and the inclined slabs inside the individual caissons are coupled together.