PURPOSE: To shorten construction term by assembling a block manufactured at a factory on a foundation pillar driven at a predetermined position, attaching it on a foundation ground, and then connecting the foundation pillar with the skeleton block to perform a foundation work and an incidental work.

CONSTITUTION: Foundation pillars 2 are driven at positions where a three- dimensional crossing bridge is installed, and bridge blocks 3 manufactured at a factory are carried to construction site and are assembled. Grout is poured on a bottom face 5 to attach the block 3 with a foundation ground 10 adhesively. After that, the foundation pillars 2 and the skeleton blocks 3 are tightened by bolts, welding, etc., to perform a foundation work. Consequently, construction term for the three-dimensional crossing bridge can be shortened, and a period of traffic regulation can be shortened greatly.