PURPOSE: To make it possible to couple building units quickly and efficiently by hanging a coupler over the upper surfaces of ceiling beams of adjacent ceiling team structural bodies of adjacent building units, and binding both ends of the coupler to each of the adjacent ceiling beam structural bodies.
CONSTITUTION: In building units 10 framed of columns 11, floor beam structural bodies 18 and ceiling beam structural bodies 20, a coupler 40 is hung over the upper surfaces of ceiling beams 15 of adjacent ceiling beam structural bodies 20 of adjacent building units 10 on the horizontal plane. Each of both ends of the coupler 40 is bount to each of the adjacent ceiling beam structural bodies 20, and the adjacent building units 10 are coupled with each other.