PROBLEM TO BE SOLVED: To provide a CO 2 supply device capable of efficiently supplying CO 2 to a plant in a cultivation room. SOLUTION: In a CO 2 supply device 1, combustion gas containing CO 2 generated by combustion of a combustor 102 is cooled and discharged by heat exchange with a heat medium flowing through a first heat exchanger 103. It has a second heat exchanger 201 which is arranged outside the cultivation room 2 and in which a heat medium circulates between the heat source machine 10 and the first heat exchanger 103, and the second heat exchanger 201 is a heat exchanger. A radiator 20 configured to exchange heat with the air outside the cultivation room 2, a supply duct 310 for supplying the combustion gas discharged from the heat source machine 10 to the plants in the cultivation room 2, and the like. To be equipped with. The supply duct 310 includes an exhaust duct 340 and a plurality of branch ducts 350 that branch from the exhaust duct 340 and have a flow path area smaller than the flow path area of the exhaust duct 340. The branch duct 350 contains combustion gas. It has a discharge port 351 to be released and is arranged so as to pass through the plant origin or the strain. [Selection diagram] Fig. 2【課題】栽培室内の植物に効率的にＣＯ２を供給でき得るＣＯ２供給装置を提供する。【解決手段】ＣＯ２供給装置１は、燃焼器１０２の燃焼により発生した、ＣＯ２を含む燃焼ガスが、第１熱交換器１０３を流れる熱媒との間の熱交換により冷却されて排出される熱源機１０と、栽培室２の外に配置され、第１熱交換器１０３との間で熱媒が循環する第２熱交換器２０１を有し、第２熱交換器２０１が熱媒と栽培室２の外の空気との間で熱交換を行うよう構成された放熱機２０と、熱源機１０から排出された燃焼ガスを栽培室２内の植物に供給するための供給ダクト３１０と、を備える。供給ダクト３１０は、排気ダクト３４０と、当該排気ダクト３４０から分岐し、排気ダクト３４０の流路面積よりも小さな流路面積を有する複数の分岐ダクト３５０とを含み、分岐ダクト３５０は、燃焼ガスが放出される放出口３５１を有し、植物の株元または株の中を通るように配置される。【選択図】図２
