To provide a curtain ventilator which forms a gap for ventilation while blocking a someone's gaze from outside.

A movable plate 2 is fitted with hinges on the line-symmetric axis of a base board 1 having a pair of line-symmetric sides, thereby being configured to allow one of the sides of the base board 1 to coincide with the side of the movable plate 2 when the movable plate 2 is rotated and superimposed on the base board 1. Curtain carrier slides 6 are attached to the side of the movable plate 2 and attachment tools 5 are attached to the side of the base board 1. When the curtain is not bent, the base board 1 is vertically hung down from a curtain rail 9 with the attachment tools 5, the movable plate 2 is erected to keep the height of the curtain carrier slides 6 coincident with that of the attachment tools 5. Then, the curtain does not droop. When the curtain is bent, the base board 1 is horizontally kept, and then, the movable plate 2 is tilted toward the separation side of curtain carrier slides 6 from the curtain rail 9. Thus, the curtain is bent to obtain the gap for ventilation, while it becomes not possible to view from out side.