Abstract: A modular plant growing device includes a main frame mounted on an upright supporting surface. The main frame is configured with an accommodating space defined by an upright rear plate, an inclined top plate extending gradually and upwardly from an upper end of the rear plate, an inclined bottom plate extending gradually and upwardly from a lower end of the rear plate, and opposite lateral plates for receiving a plant unit. The top plate is formed with an inlet unit permitting flow of liquid for plant growth into the accommodating space therethrough. The bottom plate is formed with an outlet unit disposed adjacent to the lower end of the rear plate and permitting leakage of the liquid from the accommodating space therethrough.