A subirrigation system 10 includes a water-impervious member 16, and keeps water content in soil of a cultivated land 200 in a proper state for growing a plant. The water-impervious member 16 is formed into an upper opening vessel shape, and has a water reserving function. Water is fed to an inner portion of the water-impervious member 16 from a water tank 12 via a feed water pipe 14, whereby a soil portion 26 in a gravitational water state is formed. A water level 28 of the gravitational water within the water-impervious member 16 is properly controlled to a desired water level by a water level controller 18 provided in the feed water pipe 14. The gravitational water within the water-impervious member 16 controlled to the desired water level is appropriately sucked up to the soil in an upper layer in accordance with a capillary phenomenon. Accordingly, a soil portion 30 in a capillary water state having proper water content is formed in the cultivated land 200.