PURPOSE: To easily construct rectangular body parts in wooden building by combining square timbers in a state where positions of respective grooves are mutually matched, inserting a connecting fitting into grooves opposed to each other, and driving taper pin into the center holes of pipe materials.

CONSTITUTION: Parts of pipe materials 5 are matched to the parts of round holes 2a in a state where grooves 2 are mutually matched, and the part of a plate material 6 is matched to a cut part 2b, then a connecting fitting 4 is driven into two square timbers 1 across both of them, Then, a taper pin 8 is driven into the center hole of the pipe materials 5. Since the part of pipe materials 5 are slit by slits 7, the diameters can be extened so that the pipe materials are brought in dose contact with the parts of round holes 2a of the square timbers 1, thereby, two square timbers are strongly connected to each other. Accodingly, the number of assembling process of basic rectangular bodies can be drastically decreased in comparison with that of the conventional method.