PROBLEM TO BE SOLVED: To provide a gas sensor capable of stably measuring the concentration of ammonia gas.SOLUTION: A gas sensor includes: a first chamber 101C1 having a breath inlet port 102A； a second chamber 101C2； a gas sensitive element 130 provided in the inner part of the second chamber 101C2 and a resistance value thereof changes according to the concentration of a predetermined gas included in a breath； a partition portion 120 provided between the first chamber and the second chamber and switching between a connected state and a blocked state of the first chamber and the second chamber； and a measurement part 150 for measuring the concentration of the gas based on a temporal change degree of a resistance value of the gas sensitive element 130 in a state that the breath introduced into the first chamber in a state that the first chamber and the second chamber are blocked by the partition part 120 is in a state that the first chamber and the second chamber are connected by the partition part 120 and introduced into the second chamber.SELECTED DRAWING: Figure 1【課題】アンモニアガスの濃度を安定的に測定できるガスセンサを提供する。【解決手段】ガスセンサは、呼気導入口１０２Ａを有する第１チャンバ１０１Ｃ１と、第２チャンバ１０１Ｃ２と、第２チャンバ１０１Ｃ２の内部に設けられ、呼気に含まれる所定のガスの濃度に応じて抵抗値が変化するガス感応素子１３０と、第１チャンバと第２チャンバとの間に設けられ、第１チャンバと第２チャンバとが連通された状態と遮断された状態とを切り替える仕切部１２０と、第１チャンバと第２チャンバとが仕切部１２０によって遮断された状態で第１チャンバに導入された呼気が、仕切部１２０によって第１チャンバと第２チャンバとが連通されて第２チャンバに導入された状態で、ガス感応素子１３０の抵抗値の時間的変化度合に基づいて、ガスの濃度を計測する計測部１５０とを含む。【選択図】図１
