PURPOSE: To improve overall efficiency and to shorten the term of work by assembling a beam form and timbering for supporting it in advance at a place other than the site of installation and transporting the assembly and installing it on the job site at a time desired.

CONSTITUTION: A beam form 11 made of precast concrete and timbering 12, 12 for supporting the form are assembled together in advance in one united body at a place of work other than the job site. At this time, a steel bar cage 13, main reinforcement or the like have been inserted in a U-shaped gutter 15 of the beam form 11. Next, at the time desired, these beam form 11 and timbering 12, 12 united together are transported to the job site and placed at a desired position by lifting with a crane 16 or the like. in addition, a required number of the beam forms 11 are sequentially lifted and installed thereby constituting an overall structural frame.