An object of the present invention is to accurately measure a cardiac cycle using an FM-CW radar. A standing wave, which is a composite wave of a reflected wave (reception signal) reflected from the surface of a human body P and a transmission signal, is used as an output signal using an FM-CW radar 1, and a harmonic component is removed. The output signal is subjected to Fourier transform to obtain a distance spectrum. A first-order differential signal obtained by first-order differentiation of a time waveform of a phase component of the distance spectrum is obtained, and an R-wave candidate time is obtained from the first-order differential signal. Among the time intervals of the R-wave candidate time, a time interval within the range of the resting cardiac cycle is set as a cardiac cycle candidate. Heart cycle candidates are arranged for N cycles, and a minimum error which is the difference between the time of each cycle (heartbeat candidate time) and the R-wave candidate time closest to each heartbeat candidate time is obtained. Find the sum of the minutes. The heartbeat cycle candidate with the smallest sum is defined as the average heartbeat cycle. [Selection diagram] FIG.【課題】ＦＭ－ＣＷレーダーを用いて精度良く心拍周期を計測すること。【解決手段】ＦＭ－ＣＷレーダー１を用いて、人体Ｐの表面にて反射した反射波（受信信号）と送信信号との合成波である定在波を出力信号とし、高調波成分が除去された出力信号をフーリエ変換して距離スペクトルを求める。距離スペクトルの位相成分の時間波形を１次微分した１次微分信号を求め、１次微分信号からＲ波候補時刻を求める。Ｒ波候補時刻の時間間隔のうち、安静時心拍周期の範囲内の時間間隔を心拍周期候補とする。心拍周期候補をＮ周期分配置し、各周期の時刻（心拍候補時刻）と、各心拍候補時刻に最も近いＲ波候補時刻との差分である最小誤差を求め、最小誤差の２乗のＮ周期分の総和を求める。総和が最も小さい心拍周期候補を平均心拍周期とする。【選択図】図４
