This tissue excision device has the following elements: a jaw disposed at a distal end of an insertion portion and used to sandwich tissue a cutter movable along a track formed along the shape of the jaw a drive unit which generates force to drive the cutter and a force transmission member which connects the drive unit and the cutter and accommodated in an accommodation portion provided along the track, and which transmits the force generated by the drive unit to the cutter, and the drive unit is configured to generate greater force as reaction force from the accommodation portion becomes greater.
