A hydroponic apparatus includes: a cultivation tank that encloses an underground space with a ground surface portion that separates the underground space and an aboveground space； a light applying unit that is controlled to go into either of a light period in which light is applied to the plant and a dark period in which light is not applied to the plant； an aboveground temperature detection unit that detects a temperature of the aboveground space； an aboveground temperature adjustment unit that adjusts the temperature of the aboveground space and a control unit that controls the aboveground temperature adjustment unit based on information on the temperature of the aboveground space detected by the aboveground temperature detection unit. The control unit controls the aboveground temperature adjustment unit such that the temperature of the aboveground space in the dark period is lower than the temperature of the aboveground space in the light period.
