A sun shade apparatus of the present invention has a pair of cables provided so as to be movable in outer tubes. A curtain has its opposite ends connected to ends of each cable and is stretched with the movement of the cables. At least one of the outer tubes is divided into a first tube and a second tube between which a length adjusting mechanism is interposed. The length adjusting mechanism consists of a first connecting member having a female thread formed therein, and a second connecting member having a male thread formed on its outer surface and having a cylindrical portion which is screwed into the female thread of the first connecting member. A fastening nut member which abuts against an end surface of the first connecting member is provided on the cylindrical portion.