Abstract: An invention to measure the blood pressure of a living body in a noncontact and non-invasive manner. An experimental device irradiates a subject with microwaves from a transmission antenna and a reception antenna. The phase of the reflected wave varies with micro-movements caused by the heartbeat, a pulse wave is detected from the difference between the emitted wave and the reflected wave. The experimental device detects the blood pressure from a blood pressure sensor mounted on the subject while detecting the pulse wave. A spectrum of the pulse wave of is generated by Fourier transformation. A comparison of the spectrum and the blood pressure of the subject detected by the blood pressure sensor reveals a positive correlation of the systolic blood pressure with an eighth harmonic wave from the pulse wave. A device can detect a pulse wave in a non-invasive manner using a microwave and measures systolic blood pressure.