PURPOSE: To enable coping with even a complex surface structure and lightweighting by a cylindrical ferrite core into a part of a structure reinforce ment bar of a facing PC panel.

CONSTITUTION: A cylindrical ferrite core 2 25mm long having 25mm outer diameter, and 6.1mm inner diameter is inserted into a reinforcement bar 1 6mm in diameter. This reinforcement bar 1 is welded in a 75mm mesh form and bundled to form a double-layered structure reinforcement, which is driven into a lightweight concrete 3, thereby constituting a radiowave-absorbing panel. This makes the panel lightweighted by 1/3 of the prior art. Further, arc forms and rugged forms can be manufactured by a simple process with no facing materials, and it is unnecessary to consider falling of PC panels with integrated different kinds of materials by differences in coefficient of thermal expansion.