PROBLEM TO BE SOLVED: To provide a plant growth promoting apparatus supplying nitrogen oxides at low cost.SOLUTION: A plant growth promoting apparatus 100 promoting growth of plants comprises: one or a plurality of discharge sections 112 provided at a cultivation site (green house 10) of the plants 12 and discharging electricity in the air； and a discharge control section 130 controlling one or the plurality of discharge sections 112 and maintaining a concentration of nitrogen oxides in the ambient atmosphere of the cultivation site at a target value.SELECTED DRAWING: Figure 1【課題】低コストで窒素酸化物を供給する植物育成促進装置を提供する。【解決手段】植物の育成を促進する植物育成促進装置１００は、植物１２の栽培地（温室１０）に設けられ、空気中で放電させる１または複数の放電部１１２と、放電部１１２を制御して、栽培地の雰囲気中の窒素酸化物の濃度を目標値に維持する放電制御部１３０と、を備える。【選択図】図１
