The endoscope system 1 includes an endoscope 10 having a flexible channel 14 through which the insertion portion 11 is inserted, a treatment instrument 20 inserted from the insertion port 14 A of the operation unit 12 of the endoscope 10 and passing through the channel 14 And a power source 30 for outputting high frequency power. The endoscope 10 includes a first power transmitting electrode 18 A and a second power transmitting electrode 18 B, and includes a power transmitting portion 19 for generating an AC electric field applied to the channel 14 by high frequency power , And the treatment instrument 20 includes a first power receiving electrode 28 A capacitively coupled to the first power transmitting electrode 18 A and a second power receiving electrode 28 B capacitively coupled with the second power transmitting electrode 18 B and together with the power transmitting unit 19, And a power receiving unit 29 that receives an AC electric field and constitutes a resonance circuit having the same resonance frequency.内視鏡システム1は、挿入部11を挿通する可撓性のチャンネル14を有する内視鏡10と、内視鏡10の操作部12の挿入口14Aから挿入されチャンネル14を挿通する処置具20と、高周波電力を出力する電源30と、を具備し、内視鏡10が第1送電電極18A及び第2送電電極18Bを含み高周波電力によりチャンネル14に印加される交流電界を発生する送電部19を有し、処置具20が第1送電電極18Aと容量結合する第1受電電極28Aと第2送電電極18Bと容量結合する第2受電電極28Bとを含み、送電部19とともに高周波電力の周波数と共振周波数が同じ共振回路を構成する、交流電界を受電する受電部29を有する。
