An endoscopic submucosal dissection device includes: an attachment/detachment portion that is separably attached to an insertion portion of an endoscope having an observation portion provided at the insertion portion to observe a front side a mucous membrane support portion that supports a mucous membrane a muscular layer support portion that supports the muscular layer a wire portion that is formed in a linear shape from a conductive material and is disposed so that an intermediate portion in its longitudinal direction is located at a distal end side in relation to first and second ends in the longitudinal direction and the intermediate portion is located at the distal end side in relation to the insertion portion an insulation member that exposes part of the intermediate portion of the wire portion as an electrode portion and covers an outer circumferential surface of a remaining portion of the intermediate portion of the wire portion and an operation portion that is connected to the first and second ends of the wire portion.
