A medical instrument system includes: an elongated member that has a longitudinal axis and an inner space in a direction of a longitudinal axis, and is formed in the direction of the longitudinal axis； an insertion section that is arranged at the inner space so as to freely move in the direction of the longitudinal axis and has a bending section capable of being bent； a manipulation section configured to manipulate the bending section； a first manipulation member that is connected to the manipulation section and transmits a driving force of the bending section in accordance with the manipulation by the manipulation section； a second manipulation member that is connected to the bending section and is arranged in the direction of a longitudinal axis； a connecting section capable of detachably connecting the first manipulation member and the second manipulation member； and a switching mechanism that switches between a connection state in which the first manipulation member and the second manipulation member are connected by the connecting section and a release state in which a connection of the first manipulation member and the second manipulation member is released, in accordance with a relative movement between the elongated member and the insertion section.
