To grow a plant (100) which stores nutrients synthesized in an above-ground part (A) into an underground part (B), a hydroponic cultivation apparatus (1) waters the underground part (B). The hydroponic cultivation apparatus (1) includes: a void portion (20) housing the underground part (B) while establishing a substantially sealed state a sensor (14) which detects an amount of moisture in the void portion (20) at the underground part (B) or around the underground part (B) an air conditioning fan (41) which introduces outside air to the void portion (20) and controls temperature and humidity inside the void portion (20) and a controller (3) which controls the amount of moisture detected by the sensor (14) by driving the air conditioning fan (41) in such a way as to adjust an amount of the outside air or an introduction period of the outside air.
