PROBLEM TO BE SOLVED: To provide a planting unit for planting by an underground irrigation system capable of reducing a used amount of artificial water as much as possible while effectively using non-artificial water such as rain water or the like in addition to the artificial water such as tap water or the like.SOLUTION: The planting unit 100 includes, a tray 10 with an open upper part having a deck slab 11 and a side wall 12, wherein an inside the tray 10 is divided into at least two compartments 10a and 10b by a partition 13. At least one compartment is a first compartment 10a to which at least the artificial water is provided. At least one compartment of the other is a second compartment 10b to which only non-artificial water is provided. Water guide members 20 are extended upwardly from each compartment, and a water guide mat 30 is placed on the water guide members 20 corresponding to the each compartment. The artificial water and/or the non-artificial water are provided through at least one water guide member 20 by capillarity to the water guide mat 30, and plants are planted on the water guide mat 30.
