The sensor insertion device (10) moves the sensor (12) together with the device body (18) and the insertion needle (32), thereby moving the detection unit (14) and the insertion needle (32) into the patient's body. A mechanism (20), and an indwelling member (24) that is disposed on the movement path of the sensor (12) and is attached to the sensor (12) as the movement mechanism (20) moves the sensor (12). . The indwelling member (24) is placed on the patient's skin in a state where the sensor (12) and the transmitter (16) are connected at the insertion position where the detection unit (14) is inserted into the body of the patient.センサ挿入装置（１０）は、装置本体（１８）と、挿入針（３２）とともにセンサ（１２）を移動させることで、検出部（１４）及び挿入針（３２）を患者の体内に挿入させる移動機構（２０）と、センサ（１２）の移動経路上に配置され、移動機構（２０）によるセンサ（１２）の移動にともなって該センサ（１２）に取り付けられる留置部材（２４）と、を備える。留置部材（２４）は、検出部（１４）が患者の体内に挿入された挿入位置で、センサ（１２）とトランスミッタ（１６）を接続した状態で患者の皮膚上に留置させる。
