An object is to provide a lumen passability checking device that has a simple structure and its capsule shape easily crushes after a predetermined time in a lumen so as to ensure a reliable excretion. Since an insoluble unit (42) formed of a thin film, covering a surface of a soluble unit (41), which forms a capsule-shaped structure, and exposing a part of the surface (43) as an opening, the soluble unit (41) dissolves in the lumen after the predetermined time, the insoluble unit (42) formed of the thin film then cannot maintain the capsule shape and collapses. Therefore, the excretability is reliably increased with the simple structure.
