This paper proposes a method for manipulating multiple ropes in air using a dual-arm robot equipped with three-fingered hands. The proposed method holds multiple ropes by enclosing them with three fingers. In this holding method, two modes are realized: grasping, in which the enclosed area is reduced to firmly hold the ropes, and caging, in which the enclosed area is enlarged to allow the ropes to slide. By appropriately switching between these modes, the robot repeatedly slides the grasping point to the midpoint of the rope, thereby realizing a task in which the rope is repeatedly folded in half and bundled.