To compactly fold a foldable umbrella.

A runner (5) is freely slidably provided on a flexible sliding metal rod (2), one end of a main rib (10) including four ribs (10a), (10b), (10c), (10d) pivoted to each other is pivoted (12) to an upper runner (8), the main rib (10) and the runner (5) are connected by a stretcher (22), and the respective ribs (10a), (10b), (10c), (10d) of the main rib (10) are formed to the shape of a straight line or folded in linkage with the vertical slide of the runner (5). On one side face of the third rib (10c) among the ribs of the main rib (10), the side face at one end of the second rib (10b) is piled up and pivoted. When the main rib (10) is folded, the third rib is adjacent to the side face of the second rib (10b).