A variable area frame includes: extendable arms forming each side of a polygonal frame; and a coupling mechanism that couples adjoining two of the extendable arms so that these two extendable arms can move together, in order to allow adjoining two sides of the polygonal frame to extend and contract together. Each extendable arm includes a plurality of cross units each formed by pivotally coupling two rigid members, which cross each other to form an X-shape, via a middle coupling shaft, and an end coupling portion that pivotally couples ends of adjoining ones of the cross units.
