A surgical instrument includes an insertion section, a first jaw and a second jaw provided at a distal end portion of the insertion section, having predetermined curved shapes and configured to grasp tissue； a guide section formed along the predetermined curved shape and disposed in at least one of the first jaw and the second jaw； an actuation section which is movable by being guided by the guide section； a shaft body provided at the actuation section and configured to be rotatable about a rotation axis parallel to a center line of the shaft body； and a blade section connected to the shaft body at a position apart from the rotation axis in a direction across to the shaft body and configured to be directed to the shaft body, the blade section being rotatable about the rotation axis.
