To solve problems wherein a heat insulating panel member is lifted or is peeled off a rooftop surface, and in the worst case, the heat insulating panel member is blown off because the strong wind blown from above enters a clearance between adjacent heat insulating panel members and reaches as high a place as the rooftop surface and the strong wind reaching the rooftop upper surface enters a clearance formed between a lower face of the heat insulating panel member and the rooftop upper surface, as in a case of a conventional rooftop tree planting system for heat insulation.

This rooftop tree planting system is constituted by fitting a spline tape T into spline grooves p2 formed on side faces p1a of adjacent heat insulating panel members P to connect a plurality of heat insulating panel members P mutually, arranging outer periphery protection members E1, E2 on the side faces p1a of the heat insulating panel members P constituting the outer periphery, and also arranging sealing agent V in corner parts formed by the outer periphery protection members E1, E2 and a rooftop upper surface.