PURPOSE: To raise the accuracy and efficiency of construction work by a method in which a structure oonsisting of pillars, wale and beams is formed in a wall- shaped trench excavated underground so that it can share the pressure of surround ground and water pressure and also the numbers of temporary materials are reduced.

CONSTITUTION: In a wall-shaped trench 1 excavated underground and subjected to a mud-water treatment in advance, pillars 2 are fixed at given intervals by a temporary fitting tool 24, a proper number of beams 4 are laid, a strength wall 3 is inserted and joined through a T-shaped guide rail and coupler 12 and a T-shaped tool 13, the ground inside the structure is excavated to a given flooring face 8, a foundation slab (not illustrated) is set and joined with a foundation beam 4', and a floor slab (not illustrated) is laid and connected with the beam 4. Thus, the structure can be constructed with a high accuracy and also can withstand surround soil pressure and water pressure, and the numbers of temporary structures can be reduced.