PURPOSE: To automatic all of various assembling work by providing an automatic assembling line for basic parts of a corner turning portion.

CONSTITUTION: This apparatus includes a main automatic assembling line 100 for assembling a strap 7, a connecting part and their accessary parts by use of parts of a corner turning portion. Further, the apparatus includes an automatic assembling line 200 for basic parts of the corner turning portion. The main side surface fixing installation part assembling line 100 and the corner turning portion assembling line 200 are respectively formed by modular stations disposed in parallel planes PP and P'P'.