To make it possible to perform a real-time measurement of density of measurement object gas in mixed gas of air and the measurement object gas such as a measurement of acetone density in exhaled breath and the like.SOLUTION: An output of a millimeter wave band signal oscillator 1 is distributed by a power distributor (PD) 2, while other of the output is input to an I/Q mixer 6 through a transmission antenna 3, an exhaled storage unit 4 and a reception antenna 5, is orthogonally detected by an output of the other directly input to the I/Q mixer 6, and a phase of the orthogonally detected other is detected by a phase detection unit 9. A phase difference φ of a phase θ2 when the exhaled storage unit 4 is filled with exhaled breath 21 with respect to a phase θ1 when the exhaled storage unit is filled with only air inside the exhaled breath storage unit is calculated by a phase difference calculation unit 10. Acetone density is calculated with reference to a correlationship between the phase difference φ and the acetone density by an acetone density calculation 12, and a blood-sugar level is calculated with reference to a correlationship between the acetone density and a blood-sugar level by a blood-sugar level calculation unit 14.SELECTED DRAWING: Figure 1【課題】呼気中のアセトン濃度の測定など、空気と測定対象ガスの混合ガス中の測定対象ガスの濃度の測定を小型の装置によりリアルタイムで行えるようにする。【解決手段】ミリ波帯信号発振器１の出力は電力分配器(PD)２で分配され、一方は送信アンテナ３、呼気収容部４、受信アンテナ５を経てI/Qミキサ６に入力され、直接I/Qミキサ６に入力された他方の出力により直交検波され、位相検出部９により位相が検出される。呼気収容部４内が空気のみの時の位相θ1に対する呼気２１で満たされているときの位相θ2の位相差φを位相差算出部１０で算出する。アセトン濃度算出部１２により位相差φとアセトン濃度との相関関係を参照してアセトン濃度を算出し、血糖値算出部１４によりアセトン濃度と血糖値との相関関係を参照して血糖値を算出する。【選択図】図１
