PURPOSE: To reduce construction cost by locking a step rod having upper and lower receiving beams to a large-span roof and raising the step rod with a jack installed on the upper surface of temporary post, thereby construction work being performed by taking various safety measures.

CONSTITUTION: A step rod 11, which puts a roof steel truss 8 of roof 1 between an upper receiving beam 12 and a lower receiving beam 13 and in which suspending members 25 for backup are connected to the upper and lower receiving beam 12, 13, is lifted up by a jack 10 installed on the upper surface of temporary post 6, thereby the roof 1 being raised. Next, a truss 8 is raised by installing a guide mechanism for preventing contact of truss 8 with the post 6, and is temporarily fixed to the post 6. Then, the construction work is performed by taking various safety measures; for example, a thrust support 21 is installed to the post 6, and suspending members 25 for backup are installed to the upper and lower receiving beams 12, 13 of the rod 11. This constitution can shorten the construction period.