Abstract: A beam is joined to a column by the steps of setting upright a square sleeve formed by a steel material in the shape of a box and/or square cylinder to the center of the upper surface of a base plate formed by a steel material in the shape of a plate in a posture of extending an axis in a vertical direction to connect the square sleeve to the base plate by welding, placing the base plate to the upper surface of a constructed footing through anchor bolts, inserting the lower end of a square column pipe formed by a steel material in the shape of square pipe into the square sleeve on the upper surface side of the base plate, tying the square column pipe with the connecting bolts inserted into bolt holes provided in the square column pipe and also bolt holes provided at predetermined positions of the wall surface of the square sleeve, then bringing an end plate formed by a steel material into contact with the wall surface of the square sleeve by making it condition that the end plate is preliminarily welded as on