In a bending operation apparatus provided with pinions, and two pairs of rack members connected to two pair of operation wires arranged to extend up to a bending part, where operation wires are arranged in tubular covering members, bend-preventing members which cover the operation wires in an extendable and contractable manner in driving directions of the operation wires to prevent bends of the operation wires are provided between joint portions of the operation wires with the rack members and a covering member fixing part. Further, moving ranges of the rack members are set to be changeable. Furthermore, covering member holding parts are arranged on an inner peripheral face of a connection tube part of the bending operation apparatus.
