To provide a mechanism for setting a perimeter for a sunshade device, in which perimeter columns can be set in short time, in which large force is not required, and in which the perimeter columns do not easily come off even when strong vibration such as an earthquake is generated.

This perimeter column setting mechanism 1 is composed of a perimeter column engagement member 2 engaged with a lower end part of the perimeter column 11, a lower abutment member 4 fitted and engaged with a lower pad, a guide rod 5 of which lower end part is engaged with the lower abutment member 4, and of which upper end part is inserted into the perimeter column engagement member 2, an upper abutment member 3 inserted to a middle part of the guide rod 5, an elastic member 6 provided between the upper abutment member 3 and the lower abutment member 4, and a link mechanism connecting the perimeter column engagement member 2 to the upper abutment member 3.