Contact between a face 112 to be pressed and a cam face 123 in an interaxial direction T of two inner guide sheaths 40 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 40. As a result, even in a case where external diameters Õ1, Õ2 of two inner guide sheaths 40 that form a pair are slightly different to each other, a braking member 110 can be tilted to cause a contact face 111 to simultaneously come in contact with the respective inner guide sheaths 40, and a pressing force from an eccentric cam 120 can be transmitted equally to the respective inner guide sheaths 40.
