To enable efficient greening of a roof, mitigate the heat-island phenomenon and air pollution of a city, get a large shade in summer season to attain heat-insulation effect and save the energy for cooling by training the leaves and stalks of a climbing plant planted on a planter.

A shelf 6 such as pergola is installed in a manner to cover a greening area of the roof of a building 1. Planters 20 are installed at proper parts on the roof relative to the shelf 6 and the leavest and stalks 31 of a climbing plant 30 such as wisteria 32 are trained to the shelf 6 to effect the greening of the roof.