The present invention is a plant cultivation device (99) that is provided with a cultivation tank (19) that is for growing a plant, with a water tank (30), and with a heat-collecting part (56). The water tank (30) supplies cultivation water to the cultivation tank (19) via an irrigation conduit (38). The water tank (30) also suctions cultivation water from the cultivation tank (19) via a water-sucking pipe (36). The heat-collecting part (56) has an air-storage part (57) that communicates with an upper section of the water tank (30). The heat-collecting part (56) receives sunlight (93), and the pressure of air that is heated inside the air-storage part (57) presses the surface of the water inside the water tank (30). The water tank (30) supplies cultivation water that has been pressed by said air to a culture medium material (90), which is arranged inside the cultivation tank (19), from above via the irrigation conduit (38). The heat-collecting part (56) raises the surface of the water inside the water tank (3
