To provide a compact hydroponic apparatus capable of easily utilized at outdoor section of an ordinary home, such as a balcony, throughout the year.

A hydroponic apparatus is entirely surrounded with; a step-wise insulating plates 16 comprising connection holes 16a arranged at corresponding positions to a large number of cultivation holes 10a arranged on upper surface of a cylindrical cultivation tank 10; bottom insulating plates 17 on which a nutrient tank 14 may be arranged; a fixed step-wise insulating plates 16; side insulating plates 18 which closes between the insulating plates 17 and may be opened and closed; and a back insulating plate 19. In winter, the hydroponic apparatus may be used in a closed state so as to keep the warmth by insulating it from outside air. When the nutrient 12 or the insulated air from outside air are heated with a heating device 10b, such as a heater, energy is remarkably reduced compared to a case where a domestic greenhouse is heated.