PROBLEM TO BE SOLVED: To provide a high frequency knife for endoscope which can surely swing a rod-like high frequency electrode without any loss of the advance/retreat force of an operation wire and perform the swinging operation with a small operation stroke.SOLUTION: A connection piece 8 connecting the distal end of the operation wire 7 and a link mechanism 10 (11, 12) is provided in a direction vertical to the axial direction of the distal end part of the operation wire 7, and a guide oblong hole 9 for movably guiding the connection piece 8 only in the axial direction of the distal end part of the operation wire 7 is provided on the distal end part of a flexible sheath 1.
