PROBLEM TO BE SOLVED: To provide a photosynthesis speed measuring system capable of measuring carbon dioxide concentration in order to calculate photosynthesis speed of plants with a simple configuration.SOLUTION: There is provided a photosynthesis speed measuring system 100 of plants comprising: a cover part 1 which covers target plants 9; a housing; and a sensor which measures carbon dioxide concentration inside and outside the cover part alternately, in which the sensor is provided inside the housing, and an air agitation part which agitates the flow of air flowing into the housing is provided in the housing.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2020,JPO&INPIT【課題】簡易な構成で植物の光合成速度を算出するために、二酸化炭素濃度を計測可能な光合成速度計測システムを提供する。【解決手段】植物の光合成速度計測システム100であって、対象植物9を被覆する被覆部1と、筐体と、前記被覆部内外の二酸化炭素濃度を交互に計測するセンサと、を備え、前記センサは、前記筐体内に設けられ、前記筐体の内部に、前記筐体に流入する空気の流れを撹拌する空気撹拌部が設けられる、システムが提供される。【選択図】図1