Contact between a face to be pressed and a cam face in an interaxial direction T of two inner guide sheaths is set so that a contact width H therebetween is shorter than an interaxial distance L, and so that the contact position is located between axes of the two inner guide sheaths. As a result, even in a case where external diameters of two inner guide sheaths that form a pair are slightly different to each other, a braking member can be tilted to cause a contact face to simultaneously come in contact with the respective inner guide sheaths, and a pressing force from an eccentric cam can be transmitted equally to the respective inner guide sheaths.
