PURPOSE: To efficiently and automatically carry out irrigation of many cultivation pots by arranging many planters housing a water tank and plural cultivation pots, respectively connecting water feed pipes and drain pipes connected to a water feed regulator of each planter in series and connecting one end to a water supply source.

CONSTITUTION: Many planters 20 are arranged and plural cultivation pots 10 are then placed on a water tank housed in each planter 20. Water feed pipes 32 and drain pipes 33 connected to a water feed regulator 30 of each planter 20 are further respectively connected in series and one end of the water feed pipe 32 is simultaneously connected to a supply source 40 for water or a liquid fertilizer. The water or liquid fertilizer is then periodically fed from the supply source 40 to store a prescribed amount of the water or liquid fertilizer in the water tank in each planter 20. Thereby, irrigation for the respective cultivation pots 10 is carried out. The aforementioned method is preferably used in feeding the water or liquid fertilizer to, e.g. many cultivation pots arranged near a road, etc.