A medical instrument system (1; 1A) comprising: an elongated member having a longitudinal axis and an inner space in a direction of the longitudinal axis, the elongated member formed in the direction of the longitudinal axis; an insertion section arranged at the inner space so as to freely move in the direction of the longitudinal axis, the insertion section having a bending section (115, 116) capable of being bent; a manipulation section configured to manipulate the bending section (115, 116); a first manipulation member connected to the manipulation section, the first manipulation member transmitting a driving force of the bending section (115, 116) in accordance with the manipulation by the manipulation section; a second manipulation member connected to the bending section (115, 116), the second manipulation member arranged in the direction of the longitudinal axis; a connecting section having a first connecting section arranged with the first manipulation member and a second connecting section arranged with the second manipulation member, the connecting section capable of detachably connecting the first manipulation member and the second manipulation member; and a switching mechanism having a first acting section that is configured to connect the first connecting section and the second connecting section, and a second acting section that is configured to release the first connecting section and the second connecting section from each other, the switching mechanism switching 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. an elongated member having a longitudinal axis and an inner space in a direction of the longitudinal axis, the elongated member formed in the direction of the longitudinal axis; an insertion section arranged at the inner space so as to freely move in the direction of the longitudinal axis, the insertion section having a bending section (115, 116) capable of being bent; a manipulation section configured to manipulate the bending section (115, 116); a first manipulation member connected to the manipulation section, the first manipulation member transmitting a driving force of the bending section (115, 116) in accordance with the manipulation by the manipulation section; a second manipulation member connected to the bending section (115, 116), the second manipulation member arranged in the direction of the longitudinal axis; a connecting section having a first connecting section arranged with the first manipulation member and a second connecting section arranged with the second manipulation member, the connecting section capable of detachably connecting the first manipulation member and the second manipulation member; and a switching mechanism having a first acting section that is configured to connect the first connecting section and the second connecting section, and a second acting section that is configured to release the first connecting section and the second connecting section from each other, the switching mechanism switching 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.