The transmitting unit 12 and the transmitting antenna 13 that radiate radio waves toward the heart, the receiving antenna 14 and the receiving unit 15 that receive the radio waves transmitted through the heart, or the radio waves reflected by the heart, and the radio waves received by the receiving unit 15 The estimation unit 11 estimates the volume of blood contained in the heart and the amount of change thereof based on the amplitude or phase and the specific absorption rate of the heart.心臓に向けて電波を照射する送信部１２及び送信アンテナ１３と、心臓を透過した電波、又は心臓で反射した電波を受信する受信アンテナ１４及び受信部１５と、受信部１５で受信された電波の振幅又は位相、及び心臓の比吸収率に基づいて、心臓に含まれる血液の容量やその変化量を推定する推定部１１と、を備える。
