Provided is an underground irrigation device capable of uniformly supplying irrigation water to a plurality of culvert pipes buried in cultivated land and suppressing an uneven rise of the underground water level. This underground irrigation device can supply irrigation water to cultivated land 11 through a plurality of culvert pipes 10 by supplying the irrigation water to the plurality of culvert pipes which are buried in the cultivated land and branch from a main water supply pipe for supplying irrigation water, the underground irrigation device being provided with a water distribution member 3 which is connected between the main water supply pipe 2 and the plurality of culvert pipes 10, stores the irrigation water supplied from the main water supply pipe 2, and can supply the stored irrigation water to the plurality of culvert pipes 10 at the same water head pressure.
