A surgical instrument according to one or more embodiments may include: a base； an end effector； an elongated element to drive the end effector； a flexible shaft including a distal end coupled with the end effector； a winding member provided to the base rotatably about a rotational axis orthogonal to the second surface such that the elongated element from the flexible shaft is wound around the winding member； a drive receiving member rotatable about a rotational axis orthogonal to the second surface, to receive drive for rotating the winding member； a first guide pulley； and a second guide pulley. The first guide pulley guides the elongated element drawn from the shaft toward the second guide pulley along the rotational axis of the winding member, and the second guide pulley guides the elongated element from the first guide pulley toward the winding member in a direction intersecting the rotational axis.
