An incision instrument includes an insertion section and a manipulation section. The insertion section includes a first insulating member and an incision section inserted within the first insulating member. The incision section includes a first conductive member which has a tubular shape, and in which at least an outer circumferential surface has conductivity; a second conductive member disposed in the first conductive member to be capable of protruding from and retracting to from an opening of a distal end of the first conductive member; and a second insulating member fixed to a distal end of the first conductive member and having an opening section through which the second conductive member is capable of protruding from and retracting. The manipulation section includes a manipulation main body section and a handle member.