To make a slat curtain move to close at an optimum speed by a braking function and to realize an appropriate closing motion even when an electric motor suitable for high-speed opening and closure is adopted.

After the electric motor 5 is driven by a descent control signal Sd from a processor 12 and the closing motion of the slat curtain is started, the motor 5 is stopped by an own-weight closing motion start signal SDB from the processor 12. After the stoppage, the motor 5 functions as an electric braking means DB (dynamic braking) according to a braking giving signal Eb from the processor 12 and the slat curtain is made to continue the closing motion by the combined forces of the force of inertia of the closing motion generated after the stoppage of the motor 5, the own weight of the slat curtain and the braking force generated by the electric braking means DB.