To provide a rooftop greening having settled such problems that budgetary is deficient although merit of greening is comprehended, several kinds of problems (conditions) are set when plants are cultivated on a rooftop of a building, waterproofness of the roof must be kept, the weight of plant to be cultivated is limited and drought continues in summer.

This rooftop greening comprises settling a problem by obtaining better air and supplying it into the building, resulting in increasing tenants owing to being considered that the building is supplied with fresh air and so increasing rental income. Another problem of cultivating in a pot using a culture medium instead of soil for making the whole unit lighter is settled by a method and a system afforded by further developing conventional hydroponics. Liquid supply using capillary phenomenon is introduced.