The present invention is a medical device that performs treatment on living tissue with energy such as heat, and is less invasive in order to reduce the burden on the patient. The medical device of the present invention is provided on a support member (23), an energy output unit (21) that outputs energy for treating living tissue, and a back surface of the energy output unit (21), and the support member (23). The heat insulating part (22) supported on the distal end side of the support member (23) and the energy output part of the support member (23) are provided so as to straddle the part on the base end side and the heat insulating part (22), A heat conduction member (26) that conducts heat transferred from the energy output part (21) to the heat insulation part (22) to the support member (23).本発明は、熱等のエネルギーによって生体組織に処置を行う医療機器において、患者の負担を低減するために、より低侵襲にしたもの。本発明の医療機器は、支持部材（２３）と、生体組織を処置するエネルギーを出力するエネルギー出力部（２１）と、前記エネルギー出力部（２１）の背面に設けられ、前記支持部材（２３）の先端側に支持される断熱部（２２）と、前記支持部材（２３）の前記エネルギー出力部より（２１）も基端側の部分と前記断熱部（２２）とに跨るように設けられ、前記エネルギー出力部（２１）から前記断熱部（２２）に伝えられた熱を前記支持部材（２３）に伝導する熱伝導部材（２６）と、を備える。
