Abstract: A tube distal end position detection system (1) includes a light source device (50) that emits light, a hollow tube (10) having a flow path (11) that allows a liquid to flow through, a connector (20) provided at a base end of the tube so as to allow light from the light source device to be incident on an end surface (12) at the base end of the tube, and a light emitting portion (30) provided at the distal end of the tube. Light from the light source device passes through the tube and is emitted from the light emitting portion and transmitted to the body surface.