This invention is to provide a plant cultivation mat which can be applied to those existing buildings, and which does not require large amount of time, labor and cost for its laying and removing works, and a method for laying such plant cultivation mat, as well. According to the invention, there is provided a plant cultivation mat, comprising one or a plurality of cells with water-passage ports being perforated in the vicinity of the bottom part thereof, said one or a plurality of cells constituting a mat frame disposed in a depressed form to permit the top part thereof to open, and an inwardly recessed part being formed at the lower required part of the side wall of said cell. When this plant cultivation mat is to be laid, arrangement is made as to forming a space having a required route at the inwardly recessed part of the cell so as to form a space having a required routein the inwardly recessed part of the cell. Before the plant cultivation mat is to be laid on the mat laying surface, a water holding layer is provided beforehand. It is further preferable that, at the time of filling the laying surface with this plant cultivation mat, the space having a required route is formed, and simultaneously water supply pipe is disposed in an arbitrary route in said space.