PURPOSE: To easily and efficiently assemble reinforcing bar cages and to lessen the operator's labor required for assembly.

CONSTITUTION: This device is provided with a supporting body 30A movably on rails 10, 10 and is provided with a supporting body 30B movably on rails 20, 20. The respective supporting bodies 30A, 30B are respectively provided with supporting rods 32, 33 to be placed with main bars across these rods. Rails 40, 40 parallel with the rails 10, 20 are movably provided thereon with moving holders 50. Holding grooves 51 which hold the sheared reinforcing bars in an upright state by insertion of the bottom ends of the sheared reinforcing bars therein are formed on these moving holders 50.