A device for controlling the curvature of an end section in an endoscope is provided with tension control members for regulating the tensions in the actuating wires and adjustment members for defining the maximum movement of the end section. The end section is connected by two wires extending through a flexible pipe to a manual operating section. The manual operating section has a knob by means of which a pinion gear is rotated. The pinion gear meshes with two parallel rack gears. The two wires are respectively connected to one of the ends of each of the two rack gears by means of the tension control members. Each tension control member includes a wire stopper secured to a corresponding wire end and a wire control cylinder engagable with the wire stopper but allowing the wire stopper to be freely movable within the wire control cylinder when the wire is slack. The wire control cylinders are threaded onto bolts extending from the rack gears. The adjustment members are limit screws at the opposite ends of the rack gears.