PROBLEM TO BE SOLVED: To provide an endoscope system equipped with a new signal transmission system overcoming a problem of a signal transmission system by an optical fiber while overcoming limitations of a transmission speed, which is a problem of a signal transmission system by a lead wire, which takes efficient countermeasures against heat.SOLUTION: An endoscope system includes an insertion part 6 in which an imaging unit 20 for imaging a subject and generating an image signal is disposed at the tip, and a video processor 3 for processing the image signal generated by the imaging unit 20. A signal transmission path for connecting the imaging unit 20 and the video processor 3 is composed of a waveguide path 51 for propagating a millimeter wave or a sub-millimeter wave. The waveguide path 51 is composed of a waveguide tube 51 having an internal dielectric 52 extended in a longitudinal direction so that the dielectric constant is uniform, and a metal layer 53 that is continuously extended in a longitudinal direction and covers the outer periphery of the dielectric. The internal dielectric 52 is formed by being blended with a heat conductive filler at least partially.SELECTED DRAWING: Figure 2【課題】リードワイヤによる信号伝送方式の課題である伝送速度の限界を克服しつつ、光ファイバによる信号伝送方式の課題をも克服する新しい信号伝送方式を備えると共に、効率の良い熱対策を施す。【解決手段】被検物を撮像して映像信号を生成する撮像ユニット２０が先端に配された挿入部６と、撮像ユニット２０で生成された映像信号を処理するビデオプロセッサ３と、を有し、撮像ユニット２０とビデオプロセッサ３とを結ぶ信号伝送路をミリ波またはサブミリ波を伝搬する導波路５１で構成し、導波路５１は長手方向に誘電率が均一になるように延出された内部誘電体５２と、長手方向に連続的に延出され誘電体の外周を覆う金属層５３とを有する導波管５１により構成され、前記内部誘電体５２は少なくとも一部に熱伝導性フィラーを配合する。【選択図】図２
