PURPOSE: To increase earthquake-resistant strength, to eliminate the need for special workmanship for the execution of works, to shorten the period of the execution of works and to realize low cost.

CONSTITUTION: A building body 12, a wall 14, a wall 16, an external wall 18 and floor slabs 22, 24 are constructed through a method of cast-in-place RC construction, and cogging sections 28, 30 and a section, in which the size of another material is notched off and another material is inserted into the notched-off section, are formed while being unified with the wall 14 and the external wall 18. A stair unit 54 manufactured previously in a factory, etc., and made of PC is stretched and bonded between the floor slab 22 and a floor face 26, and a stair landing unit 32 made of PC is stretched and combined to the cogging section 30. A stair landing unit 90 made of PC is stretched and connected between the stair landing unit 32 and the floor slab 22, and a stair landing unit 92 made of PC is stretched and bonded between the stair landing unit 32 and the floor slab 24. The process is repeated subsequently, and stairs are upwards executed successively. Lastly, a roof unit 52 made of PC is stretched over the section, in which the size of another material is notched off and another material is inserted into the notched-off section. thus completing stair structure 10.