The deep thermometer (1) includes a substrate (2), a heat input terminal (3) from which heat from the subject (O) is input, and is divided into a first heat flow Ipa and a second heat flow Ipb, and flows out. A first heat flow measuring system (5) capable of measuring the first heat flow Ipa using the input side temperature sensor (6) and the first output side temperature sensor (8), the second input side temperature sensor (12) and the first Between the second heat flow measurement system (11) capable of measuring the second heat flow Ipb using the two output side temperature sensor (14), and between the heat input terminal (3) and the first input side temperature sensor (6). A first thermal resistor (10) provided and a second thermal resistor (16) provided between the heat input terminal (3) and the second input side temperature sensor (12) are provided. The deep body thermometer (1) estimates the deep body temperature Tcore of the subject (O) based on the first heat flow Ipa and the second heat flow Ipb flowing out from the subject (O).深部体温計（１）は、基板（２）と、被検体（Ｏ）からの熱が入力され第１熱流Ｉpaと第２熱流Ｉpbとに分流されて流出する熱入力端子（３）と、第１入力側温度センサ（６）と第１出力側温度センサ（８）とを用いて第１熱流Ｉpaを測定可能な第１熱流測定系（５）と、第２入力側温度センサ（１２）と第２出力側温度センサ（１４）とを用いて第２熱流Ｉpbを測定可能な第２熱流測定系（１１）と、熱入力端子（３）と第１入力側温度センサ（６）との間に設けられた第１熱抵抗体（１０）と、熱入力端子（３）と第２入力側温度センサ（１２）との間に設けられた第２熱抵抗体（１６）とを備えている。深部体温計（１）は、被検体（Ｏ）から流出する第１熱流Ｉpaと第２熱流Ｉpbとに基づいて、被検体（Ｏ）の深部体温Ｔcoreを推定する。
