PROBLEM TO BE SOLVED: To improve reliability of a measurement result of a substance in a living body when a specific substance existing in the living body is directly measured in the living body without being taken out of the body. To provide a measuring catheter. A measuring catheter (10) having a sensor (16) that is inserted into a living body and detects a substance on a wall surface (29) of a living body cavity (17), and is an approach mechanism that brings the sensor (16) close to the wall surface (29) of the living body cavity (17). 26 is provided. [Selection diagram] Figure 1【課題】生体内に存在する特定の物質を、体外に取り出すことなく、生体内で直接に測定する場合に、生体内における物質の測定結果の信頼性を向上させることができる、新規な構造の測定用カテーテルを提供すること。【解決手段】生体内へ挿入されて生体内腔１７の壁面２９の物質を検出するセンサ１６を備えた測定用カテーテル１０であって、センサ１６を生体内腔１７の壁面２９へ接近させる接近機構２６が設けられている。【選択図】図１
