A treatment instrument for endoscope that is suitable for cutting submucosal layer in endoscopic submucosal dissection is provided, and the treatment instrument for endoscope has a treatment section at a distal end of an insertion section which is inserted in a body. The treatment section includes a conductor that is connected to a high-frequency source, and is configured to have a sandwich structure in which the conductor is sandwiched between a non-conductor on the distal end side thereof and a non-conductor on a proximal end side thereof. The conductor is formed to be exposed in a strip-shape at a side surface of the treatment section, and a lateral movement of the treatment section causes a cutting of a submucosal layer with the conductor to be performed.
