The slack correction mechanism includes a distal-end pulley that is rotatable with respect to a given axis, a distal-end wire wound around the distal-end pulley, a first supporting part including a first base, a first friction portion around which the distal-end wire is looped on one side and a first biasing portion that biases the distal-end wire in a pulling direction on one end side with respect to the first friction portion, the first supporting part being adapted to support one side of the distal-end wire, and a second supporting part including a second base, a second friction portion around which the distal-end wire is looped on the other side and a second biasing portion that biases the distal-end wire in a pulling direction on the other side with respect to the second friction portion, the second supporting part being adapted to support the other side of the distal-end wire.