A device for checking indwelling site capable of checking the indwelling site of a medical tube through multiple checking operations by simple techniques using a single device is disclosed. The device for checking indwelling site is provided with a barrel, a first plunger having a torso member and a hole formed communicating between the inner cavity of the torso member and the inner cavity of the barrel and disposed capable of pushing into or pulling out while keeping the barrel airtight, a second plunger having a second tip member and disposed capable of pushing into or pulling out while keeping the torso member airtight, a space formed between an inner wall and the tip face of the first tip member and designed to suck the gas fraction of the fluid sucked into the barrel into the torso member, and a detecting member arranged inside the torso member on the tip side of the second tip member and designed to react with carbon dioxide sucked in through the space by discoloring.
