PURPOSE: To surely reciprocate a curtain when it is automatically opened or closed and move the curtain with light acting force when it is manually opened or closed.

CONSTITUTION: A runner 2 is supported on a rail 7 provided at the upper end of a window. A curtain 1 is hung from the runner 2, and the runner 2 stores a solenoid 5 in it. When the solenoid 5 is operated interlockingly with the rotating motor 4 of a runner moving body 3, a coupling pin 51 is protruded from the runner 2, and it is coupled with the recess 31 of the runner moving body 3. When the motor 4 is stopped, the coupling pin 51 is submerged into the runner 5 and released from the recess 31, and the curtain 1 can be manually opened or closed.