To make a long guide rail for curtain compact so as to facilitate the storage, transportation, and carrying and to improve the mounting workability on a window frame by dividing a guide rail main body in a plurality of sections in the longitudinal direction and connecting end parts mutually by expandable connector in series.

A guide rail main body 1 is provided with a guide groove along a central part of a lower face, and cases 11, 12 are fitted externally and fixed at both ends so as to cover open ends. The guide rail main body 1 is divided into two parts in a central part in the longitudinal direction, and end parts of the divided guide rail divided bodies are mutually connected by a hinge plate 1f which is an expandable connection tool over a back plate 1a thereof so as to bend it. Two head runners 3, 4 connected with a head part of a curtain 5 and an idle runner supporting an upper end fringe in an intermediate part of the curtain 5 are slidably fitted into this guide rail main body 1 in play, and a string 2 stretched over a winch 13, a pulley 14, and leading runners 3, 4 is provided like a loop.